Anti-frogman techniques
Encyclopedia
Anti-frogman techniques are security methods developed to protect watercraft
, port
s and installations, and other sensitive resources both in or nearby vulnerable waterways from potential threats or intrusions by frogmen or other divers
.
this need for military underwater security was first shown by the achievements of frogmen against armed forces facilities: see for example Italian frogman actions in WWII. Since the late 1950s, the increasing demand for and availability of sophisticated scuba diving
equipment has also created concerns about protecting valuable underwater archaeology
sites and shellfish
fishing stocks.
The 12 October 2000 USS Cole bombing
was not carried out by underwater divers, but did bring renewed attention to the vulnerability they present for naval ships. Divers can swim 100 to 200 yards in three minutes time, and large sonar
ranges would need to be established around ships in order for security forces to detect underwater swimmers in time to make a sufficient response.
In March 2005 the Philippine military, interrogating a captured anti-government terrorist bomber
, found that two of Southeast Asia
’s most dangerous terrorist organizations linked to Al Qaeda were said to be jointly training militants in scuba diving for attacks at sea.
Hereinafter, "nlsn" = "Non-Lethal Swimmer Neutralization Study"
Swimmers can approach from the surface or underneath the waters, the two presenting their own detection and deterrence challenges. And the interception and apprehension of intruders detected in bodies of water pose unique safety risks.
There are various types of places of operation:
There are these likely theaters of operation:
In most scenarios nowadays #1 or perhaps #2 is likelier, but in war or semi-war conditions or where there is a risk of terrorism
#3 may be likelier than usual.
A police-type technique that is reasonably safe on land may be risky to a scuba diver.
The document nlsn leans strongly towards #1, and discusses only non-lethal weapons. But in war and semi-war situations there is more risk of #3 and the choice may be for lethal weapons.
since the mid-1950s, making it bad policy for most democracies to use potentially lethal methods against any suspicious underwater sighting or sonar echo in areas not officially closed to sport divers. Any routine patrol investigation of all "unidentified frogman" reports would have had to stop because any genuine reports of intruders would be swamped in ever more reports of civilian sport divers who were not in military areas.
For a long time it would be easy for diving professionals and other experienced divers to distinguish a sport diver with an open-circuit scuba such as an aqualung
from a combat frogman with a rebreather
; and legitimate civilian divers are normally fairly easy to detect because they dive from land or from a surface boat, rarely or never from an underwater craft, and willingly advertise their presence for their own safety.
However, particularly in former years when scuba diving was less common, many non-divers, including many police and other patrol and guard types, knew little about diving and did not know of this difference in diving gear, but described all divers as "frogmen"; one result was an incident in the inter-ethnic crisis in Cyprus
in 1974 when a tourist was arrested for suspected spying because "frogman's kit" was found in his car: it was actually ordinary sport scuba gear.
After about 1990 the rapid growth in the number of sport diving rebreather brands has clouded this distinction, while advanced sport divers increasingly tackle longer deeper riskier dives using equipment once available only to armed forces or professionals. This means that even "less-lethal" techniques for trapping them underwater, disorienting them, or (especially) forcing them to the surface would be an ever-increasing risk to civilian divers' lives.
In former times, civilian diving was only for work, and needed standard diving dress
and big easily seen surface support craft. Sport scuba diving has changed that.
Some naval personnel object to civilian divers getting into waters being used for armed forces exercises, or consider any sport diving as intruding into naval and work divers' territory, and may be tempted to take their own action against the "intruders".
Another result of sport diving is a risk of civilians independently re-developing, and then using or selling on the free market, technologies, such as technical advances in underwater communications equipment, heretofore kept as military secrets. (For a loss of military secrecy caused by independent civilian duplication (though not underwater), see Lokata Company.)
There have been incidents which have demonstrated poor underwater security, when a sport diver with a noisy bubbly open-circuit scuba and no combat training entered a naval anchorage and signed his name on the bottom of a warship
. Concern at the risk of increasing the sport-diving public's ability to penetrate harbors undetected, and of unofficial groups equipping combat frogmen from the sport scuba trade, might have led to the events listed at "#Prevention" below.
) is a United States Coast Guard
harbor and inshore patrol and security team whose methods include detecting submerged divers.
.
when there is the least amount of moonlight.
Open circuit scuba bubbles can make detection easy, but not easily in rough foamy sea water.
Swimming deep can hide from surface guards; but if the underwater visibility is good, he may have to go deeper than is safe with an oxygen rebreather, and with open circuit scuba he makes more bubbles at each breath in proportion to (depth + 10 meters) = (depth + 33 feet).
range may improve detecting surface swimmers at night, but this idea is not yet tested..
and electronic neural network
s and developments in ultrasound
have made possible specialized diver-detector sonars.
Experience has showed that passive sonar (i.e. merely listening for underwater sounds) cannot detect everything; in particular it cannot easily detect rebreather divers and unequipped surface swimmers; and it can detect direction, but not distance unless readings from two or more listening stations can be correlated.
High-power low-frequency sonar commonly used for depth sounding and to detect large objects (including submarines) is not good at detecting small objects like divers, but the US Navy Diving Manual 24 says that it is hazardous to divers.
Examples of diver-detecting active sonar systems are:
s and sea lion
s can find submerged divers. Both can see, and hear direction of sound, well underwater, and dolphins have natural sonar
..
The United States Navy’s MK6 Marine Mammal System is supported by SPAWAR and uses dolphins to find and mark mines and divers in the water. This system was used in:
Animals, unlike remotely operated underwater vehicles (ROV), etc., need to be fed and kept fit and in training whether they are needed at work or not, and cannot be laid aside in a storeroom until needed.
This link reports that: In 1970 to 1980 trained dolphins killed 2 Russian frogmen who were putting limpet mine
s on a USA cargo
ship in Cam Ranh
bay in Vietnam
. After that, Russian frogmen were trained to fight back against trained dolphins, and in an incident on the coast of Nicaragua
Russian frogmen killed trained anti-frogman dolphins.
In some circumstances, submerged open-circuit scuba divers can be followed by their bubbles until they run out of air and have to surface, and then tackled on the water surface or as they come ashore.
According to circumstances, the patrol may need some means of transporting prisoners and/or seized diving equipment away from site.
Many casual sport diving intruders may keep away on seeing visible clearly marked patrol boats and surface barriers.
Shotgun
s (probably pump-action
, when used as a security squad weapon) may be effective when the target is out of water, but are even less useful underwater.
Special underwater firearm
s have been designed for use underwater: see #Underwater firearms below
is effective, and may be lethal, but may cause other damage underwater, and is not recommended in peacetime when the victim may be an intruding civilian sport diver, although it is alleged to have been common practice for some years after 1945 in British naval harbors.
Divers, however, are far less vulnerable to damage by underwater explosion than common sense would dictate. Since the tissues of the body tend to transmit the shock waves with much the same characteristics as the water around, large distant shocks have little impact on divers. For this reason, the most effective "depth charge" for use against a diver is the common hand-grenade, tossed within a few feet of the diver. The resulting gas cavitation and shock-front-differential over the width of the body is effective in stunning or killing the diver.
does not work underwater, as water absorbs microwave
s well (as in microwave cookers).
misread is possible. Such a magnetic coil carried by a patrol boat directly over the target diver would affect compass readings to 5 meters (15 feet) depth at about 7 kilowatts; but to 10m (30 feet) (oxygen rebreather depth limit) at about 448 kilowatts, which is too much power need to be practical.
There has been much research about the effect of sound on divers. See the bibliography
in nlsn (page 51 etseq, 356 entries).
The US Navy Diving Manual(page 24) says that high-power low-frequency sonar (commonly used for depth sounding and to detect large objects (including submarines)) is not good at detecting small objects like divers, but is hazardous to divers. At high enough power it could be a reliable lethal anti-diver weapon.
on the human body are heating and cavitation
. See nlsn(pages 21–23) for detailed information. Also see ultrasound
and sonic weaponry
.
As each wave of the ultrasound passes through the diver, any bubbles in the tissue expand and contract, and the tissue heats. After a particular threshold of loudness of the ultrasound, new bubbles form during the low-pressure part and disappear during the high-pressure part: this is cavitation
and can cause injury.
One well-known method is a powerful blast from a ship's ordinary high-power low-frequency sonar
(commonly used for depth sounding and to detect large objects (including submarines)), which deranges the diver's inner ear
and makes him dizzy and disoriented and tends to force him to surface, or may make him panic and lose his mouthpiece and drown. These large "active sonars" are used to search for submarines and are very powerful. These sonars are usually bow mounted, and if so a diver attacking at the stern would be in the sonar baffle region and unaffected, if he gets close enough first.
Most ships, both military and non-military, carry smaller "navigation" sonars such as depth finders or collision sensors, but their high frequencies and relatively low power lack effectiveness against divers.
A test of a 230 decibel 3000 to 7000 Hz transmitter killed seven whales, causing hemorrhages around their ears: see Sonar#Sonar and marine animals - adverse effects.
Around the 1970s there were reports among sport scuba divers from offshore from a Ministry of Defence
area in Dorset
in England
of diver deaths, mass deaths of fish, and divers returning reporting "strange sonic noises": they speculated about a secret anti-frogman weapon, but it may have been merely a powerful modulated ultrasound
beam intended to communicate with submarine
s.
Some say that these speculations are mostly fanciful and that since the human body is very close to the impedance of the water around it, the ultrasound tends to pass through the body (perhaps breaking the eardrum, but not killing the diver); but if the sound or ultrasound is powerful it may cause overheating or cavitation damage on the way.
Some say that most deaths of people in the water from sonar have come from a freak combination of the diver's physical condition with local acoustic reflection of high-powered audible sonar that uncharacteristically "focused" the sound on the diver, or matched the resonant frequency of the diver's air cavities.
However:
It is unknown what later proof or disproof there has been of speculations such as appeared in a book about Cousteau
written by Philippe Diole
around 1960, about underwater ultrasound guns making an ultrasound
beam powerful enough to disintegrate a diver into the water except the metal parts of his kit.
A sound that irritates or causes pain. Diver aversion to low frequency
sound is dependent upon sound pressure level and center frequency
.
Westminster International have also implemented this but they withhold the exact sound frequencies used: see http://www.wi-ltd.com/defence/Maritime_Defence/Acoustic_Defence_Systems/Enforcer_Underwater_CommunicationDiver_Disruption_System .
The sound may be an order to surrender or surface or go onshore or to the patrol boat, perhaps with a threat to use non-lethal or lethal force if disobeyed. But such an order must be clear enough to be heard and understood.
Underwater, human hearing is largely by bone conduction
, through the skull and not through the eardrum
and ossicles. This causes somewhat less acuity of hearing and a different graph of sensitivity against frequency, with a loss between 1000 Hz and 5000 Hz. This may affect ability to understand speech.
Research showed that, at depths up to at least 10m (30 feet), divers' wetsuit
hoods lessened underwater hearing sensitivity by 10 to 35 decibel
s at 1000 Hz and above, and by little or nothing at 250 Hz and below. With increasing depth in a hyperbaric chamber, decreases in wetsuit hood sound attenuation appear only to occur at frequencies between 500 and 1500 Hz. In the open ocean, hood attenuation at 8,000 Hz showed a significant decrease at 60 fsw and a tendency to decrease at 2,000 and 4,000 Hz compared with the 10 fsw data at the same frequencies in the chamber trials. At frequencies from 500 - 4,000 Hz wetsuit hood sound attenuation was on average 8 dB lower in the ocean than in the chamber trials.
Underwater, humans are much less able than in air to tell where a sound came from. Research showed that what ability remains is better with bang!-type noises than with pure tones.
caused vibration, and at high powers cavitation
and damage.
s, and at high power causes discomfort from vibration in the lungs.
Loud sound in this frequency range was difficult to make, but the plasma sound source should make it easier; divers found plasma sound source noise underwater "very unpleasant".
disappearance speculated about underwater electric shock weapons mounted on warships to defend them from frogmen. This method, if it is used, imitates nature; see electric eel
and electric ray
.
, commonly in comics. Some sorts might be possible if designed.
Small dredging-type craft and small submarine
s are used for small-scale dredging and/or to recover submerged objects; but there is no known case in the real world of them being used to capture divers. The craft's capture device might be a net or a grab or an aimable suction tube or a scoop.
can sometimes be used to catch submerged divers.
This agrees with talk among diving circles about a fishing trawl being the handiest way for naval men to get unwelcome or unauthorized divers out of the water.
An article at the American Academy of Underwater Sciences
1991 International Symposium
Proceedings says that the California Department of Fish and Game
, to capture sea otter
s underwater for a relocation
program, successfully used a net cage apparatus front-mounted on a Dacor
Scooter diver propulsion vehicle
steered by a diver with a silent bubbleless closed circuit oxygen rebreather
. It is not known if a similar larger device has ever been used to capture divers underwater.
.
A text fiction story (The Deep Range
by Arthur C. Clarke
) mentioned a diver-catching grab
used to recover a work diver suffering from nitrogen narcosis
, not to arrest a suspect; presumably, it is easier to rescue an impaired diver than to apprehend an unimpaired one, but it could be adapted if combined, for instance, with a stunning device.
Grab-type devices on various scales are very commonly used in nature underwater by animals. The device is usually its jaw
s, but in some animals evolution
converted leg
s into arm
s to handle objects; see Opabinia
for a very early example of a nose turned into a grab.
There have been cases of unofficial groups dragging a grapnel behind a fishing boat through a group of submerged scuba divers.
Such devices on a small scale are sometimes used in nature to catch prey: for example by the seahorse
and the pipefish
, and the bladderwort
plant. The mouths of many teleost
fish
(for example centrarchid
s) have a strong suction component to the way they work.
This make is metal chain-link netting placed underwater, preventing entry into an area, or at least delaying the frogmen while they cut through it.
It was made by a Swedish
company, Safe Barrier Systems (SBS), a division of NCC Stockholm. It is rigid metal netting, covered in polyethylene
electrical insulation
, and polyurethane
abrasion protector outside that. The strands are electrified so that any frogman attack on the net will be detected by that strand going open-circuit (not to electrocute him). The grid size best suited to deter divers is 250 x 250 mm = 10 x 10 inches. Testing in the UK showed that a diver using bolt cutters could cut a hole big enough to swim through in 60–90 seconds.
It was found that the net could be evaded by climbing over it, or getting under it, or by using a wire loop to complete the circuit where he cuts each strand.
The net system can be equipped with a gate (operated by an air compressor), to allow traffic in and out of the protected area.
SBS currently supports 15 sites with "Safe Barrier" nets, including four with gates, but they are not making this net system now, due to lack of demand. The price quote for a new net was more than $7,000,000.
This make is or was made by BEI Security Systems. Its system that alarms if cut is fiber-optic.
This make was made by a U.K. company. It incorporated a system that set off an alarm when its fiber-optic mesh was cut. This make seems to have disappeared, and the tradename "Aquamesh" is now used for underwater wire mesh used in the aquaculture
industry for lobster and crab traps.
However, underwater combat between opposing teams of frogmen (although common in fiction (as in the movie Thunderball
, and The Silent Enemy, and at least one incident in Sea Hunt
), and often in comics) is unusual in reality.
Sometimes diving sea-police have arrested civilian divers for illegal spearfishing
and diving in restricted areas and the like, and naval divers have been sent down to investigate unidentified divers in a naval harbour.
When confronted, sport divers are likelier to obey the patrol divers quietly as ordered; hostiles would be likelier to fight back.
Among the ways suggested of forcing arrested divers to surface would be attaching an inflatable float to each.
Objections to the likelihood of this tactic are:
If the patrol divers are riding suitable diver propulsion vehicle
s, they could travel faster and carry better weapons (lethal or non-lethal) and equipment for sonar search and navigation and communication, and perhaps a means (e.g. grab or net) to capture suspect divers in passing and tow them alongside back to the base or patrol boat.
It was thought expensive for a team of patrol divers to be on standby all the time kitted up to dive; but France
has police
divers trained to arrest unauthorized or suspect divers underwater and to force them to surface. One common offence there is or was spearfishing
while using breathing apparatus.
See Frogman#Equipment for features useful in equipment of frogmen who may get into underwater fights.
The Russian PDSS
system is an example of an anti-frogman defence system which includes frogmen trained in underwater fights.
See Russian commando frogmen
under "1970 and after" for a report of a real underwater fight between a guard squad of Russian PDSS frogmen and intruding enemy frogmen.
The films Above Us the Waves and The Silent Enemy are reconstructions of real World War II
events, and each shows an underwater fight between opposing groups of frogmen, but those fights did not happen in the real events.
s for frogmen to use as a lethal weapon; there is said to have been a real incident when Russian frogmen shot two anti-frogman dolphins.
These underwater firearms fire a steel rod, not a bullet, for better range underwater. They are all more powerful than a speargun
, and can fire several shots before reloading. Their barrels are not rifled
; the fired projectile is kept in line underwater by hydrodynamic effects, and is somewhat inaccurate when fired out of water.
The rifles are more powerful than the pistols (and look more impressive in frogmen's group photographs), but the pistols are more easily swung sideways quickly underwater at a target.
s trained to carry on the nose a device which injects a large amount of compressed carbon dioxide
into the frogman. This would likely be lethal due to blood embolism
. It is said that they were trained at Point Mugu. It was said that this device was abandoned because of fears that wild dolphins might imitate and start harassing ordinary divers. Today the mammals are primarily trained to force the diver to the surface using pushing techniques in the assumption that the majority of incursions can be addressed in this manner.
This link says that the US Navy has deployed sea lion
s to detect divers
in the Persian Gulf
. The sea lion is trained to detect the diver, connect a marker buoy
to his leg by a C-shaped handcuff-like clamp, surface, and then bark loudly to raise the alarm. 20 sea lions have been trained for this at the US Naval Warfare Systems Center in San Diego. Some have been flown to Bahrain
to help the Harbor Patrol Unit to guard the US Navy's 5th Fleet. Sea lions adapt easily to warm water, can dive repeatedly and swim up to 25 mph, can see in near-darkness, and can tell where sound comes from underwater. In training the sea lions have been known to chase divers onto land. See also this link.
This link reports that in 1970 to 1980 trained dolphins killed 2 Russian frogmen who were putting limpet mine
s on a USA cargo
ship in Cam Ranh
bay in Vietnam
. After that, Russian PDSS frogmen were trained to fight back against trained dolphins, and in an incident on the coast of Nicaragua
PDSS frogmen killed trained anti-frogman dolphins. Arrival of underwater rifles and pistols seems to make the trained animal threat less.
Animals, unlike ROV
s etc., need to be fed and kept in training whether they are needed at work or not, and cannot be laid aside in a storeroom until needed.
, as well as searching, could be equipped to arrest or attack divers on command, but with their technology as it is could not attack several targets one after another as quickly as a marine mammal. A surface-only ROV would need a long-range weapon to be effective against deeply submerged suspect divers.
may be called for by the military to keep sport divers away from secret underwater sites, or by inshore fishermen to stop alleged poaching of shellfish
.
The U.S. has made many such regulations to protect such infrastructure
s as power plant and nuclear plant water intakes and discharges, bridge foundations, harbor and pier installations, and naval facilities.
The Socialist Federal Republic of Yugoslavia
(until it broke up) forbade all sport diving except a few Government-controlled groups, and required official permission for each campaign of archaeological or scientific diving.
Watercraft
A watercraft is a vessel or craft designed to move across or through water. The name is derived from the term "craft" which was used to describe all types of water going vessels...
, port
Port
A port is a location on a coast or shore containing one or more harbors where ships can dock and transfer people or cargo to or from land....
s and installations, and other sensitive resources both in or nearby vulnerable waterways from potential threats or intrusions by frogmen or other divers
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
.
Risks and threats to be defended against
In World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
this need for military underwater security was first shown by the achievements of frogmen against armed forces facilities: see for example Italian frogman actions in WWII. Since the late 1950s, the increasing demand for and availability of sophisticated scuba diving
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
equipment has also created concerns about protecting valuable underwater archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...
sites and shellfish
Shellfish
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
fishing stocks.
The 12 October 2000 USS Cole bombing
USS Cole bombing
The USS Cole Bombing, or the USS Cole Incident, was a suicide attack against the United States Navy destroyer on October 12, 2000 while it was harbored and refueled in the Yemeni port of Aden. Seventeen American sailors were killed, and 39 were injured...
was not carried out by underwater divers, but did bring renewed attention to the vulnerability they present for naval ships. Divers can swim 100 to 200 yards in three minutes time, and large sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
ranges would need to be established around ships in order for security forces to detect underwater swimmers in time to make a sufficient response.
In March 2005 the Philippine military, interrogating a captured anti-government terrorist bomber
Bomber
A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...
, found that two of Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
’s most dangerous terrorist organizations linked to Al Qaeda were said to be jointly training militants in scuba diving for attacks at sea.
Hereinafter, "nlsn" = "Non-Lethal Swimmer Neutralization Study"
Scenarios and considerations
Following World War II, the increasing popularity in recreational diving introduced a new complexity to underwater security. Divers must not only be detected, but evaluated as to their purpose or intentions for swimming in monitored areas. Steps to protect against threat or harm from divers must take into account possible reasons why they would be swimming in monitored areas. The divers may be:- Recreational swimmers without harmful intent, or
- Poachers removing sea life or valuable objects from the sea bed illegally, or
- Threats intent on sabotageSabotageSabotage is a deliberate action aimed at weakening another entity through subversion, obstruction, disruption, or destruction. In a workplace setting, sabotage is the conscious withdrawal of efficiency generally directed at causing some change in workplace conditions. One who engages in sabotage is...
or intelligence gatheringReconnaissanceReconnaissance is the military term for exploring beyond the area occupied by friendly forces to gain information about enemy forces or features of the environment....
involving sensitive water targets
Swimmers can approach from the surface or underneath the waters, the two presenting their own detection and deterrence challenges. And the interception and apprehension of intruders detected in bodies of water pose unique safety risks.
There are various types of places of operation:
- a) Underwater.
- b) On the surface of water.
- These two scenarios are discussed by nlsn.
- c) In small boats (e.g. RIBRigid-hulled inflatable boatA rigid-hulled inflatable boat, or rigid-inflatable boat is a light-weight but high-performance and high-capacity boat constructed with a solid, shaped hull and flexible tubes at the gunwale. The design is stable and seaworthy...
s) being used by unauthorized or suspect divers. - d) In larger boats being used by unauthorized or suspect divers.
- e) Arresting suspect divers onshore, before or after they dive.
There are these likely theaters of operation:
- a) In an enclosed security area, e.g. a harbor.
- b) In open water to protect submerged valuables (usually undersea archaeological sites).
- c) In open water (often on a frontierFrontierA frontier is a political and geographical term referring to areas near or beyond a boundary. 'Frontier' was absorbed into English from French in the 15th century, with the meaning "borderland"--the region of a country that fronts on another country .The use of "frontier" to mean "a region at the...
) to prevent underwater smugglingSmugglingSmuggling is the clandestine transportation of goods or persons, such as out of a building, into a prison, or across an international border, in violation of applicable laws or other regulations.There are various motivations to smuggle...
. - d) In open water to protect sea life. (This, on a small scale, may be defined to include various known unofficial actions by inshore fishermen to protect their shellfish stocks.)
- e) To prevent unofficial divers from getting in the way of other water or shore users.
In most scenarios nowadays #1 or perhaps #2 is likelier, but in war or semi-war conditions or where there is a risk of terrorism
Terrorism
Terrorism is the systematic use of terror, especially as a means of coercion. In the international community, however, terrorism has no universally agreed, legally binding, criminal law definition...
#3 may be likelier than usual.
A police-type technique that is reasonably safe on land may be risky to a scuba diver.
The document nlsn leans strongly towards #1, and discusses only non-lethal weapons. But in war and semi-war situations there is more risk of #3 and the choice may be for lethal weapons.
Sport divers and underwater security
Keeping underwater security against frogman intrusion has been complicated by the expansion of sport divingScuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
since the mid-1950s, making it bad policy for most democracies to use potentially lethal methods against any suspicious underwater sighting or sonar echo in areas not officially closed to sport divers. Any routine patrol investigation of all "unidentified frogman" reports would have had to stop because any genuine reports of intruders would be swamped in ever more reports of civilian sport divers who were not in military areas.
For a long time it would be easy for diving professionals and other experienced divers to distinguish a sport diver with an open-circuit scuba such as an aqualung
Aqua-lung
Aqua-Lung was the original name of the first open-circuit free-swimming underwater breathing set in reaching worldwide popularity and commercial success...
from a combat frogman with a rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
; and legitimate civilian divers are normally fairly easy to detect because they dive from land or from a surface boat, rarely or never from an underwater craft, and willingly advertise their presence for their own safety.
However, particularly in former years when scuba diving was less common, many non-divers, including many police and other patrol and guard types, knew little about diving and did not know of this difference in diving gear, but described all divers as "frogmen"; one result was an incident in the inter-ethnic crisis in Cyprus
Cyprus
Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the...
in 1974 when a tourist was arrested for suspected spying because "frogman's kit" was found in his car: it was actually ordinary sport scuba gear.
After about 1990 the rapid growth in the number of sport diving rebreather brands has clouded this distinction, while advanced sport divers increasingly tackle longer deeper riskier dives using equipment once available only to armed forces or professionals. This means that even "less-lethal" techniques for trapping them underwater, disorienting them, or (especially) forcing them to the surface would be an ever-increasing risk to civilian divers' lives.
In former times, civilian diving was only for work, and needed standard diving dress
Standard diving dress
A standard diving dress consists of a metallic diving helmet, an airline or hose from a surface supplied diving air pump, a canvas diving suit, diving knife and boots...
and big easily seen surface support craft. Sport scuba diving has changed that.
Some naval personnel object to civilian divers getting into waters being used for armed forces exercises, or consider any sport diving as intruding into naval and work divers' territory, and may be tempted to take their own action against the "intruders".
Another result of sport diving is a risk of civilians independently re-developing, and then using or selling on the free market, technologies, such as technical advances in underwater communications equipment, heretofore kept as military secrets. (For a loss of military secrecy caused by independent civilian duplication (though not underwater), see Lokata Company.)
There have been incidents which have demonstrated poor underwater security, when a sport diver with a noisy bubbly open-circuit scuba and no combat training entered a naval anchorage and signed his name on the bottom of a warship
Warship
A warship is a ship that is built and primarily intended for combat. Warships are usually built in a completely different way from merchant ships. As well as being armed, warships are designed to withstand damage and are usually faster and more maneuvrable than merchant ships...
. Concern at the risk of increasing the sport-diving public's ability to penetrate harbors undetected, and of unofficial groups equipping combat frogmen from the sport scuba trade, might have led to the events listed at "#Prevention" below.
Detection
The MSST (Maritime Safety and Security TeamMaritime Safety and Security Team
A Maritime Safety and Security Team or MSST is a United States Coast Guard anti-terrorism team established to protect local maritime assets...
) is a United States Coast Guard
United States Coast Guard
The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...
harbor and inshore patrol and security team whose methods include detecting submerged divers.
On the surface
A swimmer on the surface of the water is liable to detection by the same means as used on land, e.g. eyesight, surveillance cameras, thermal imaging, radarRadar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
.
Relying on eyesight from land or from surface patrol boats
In World War II this was the main precaution. That is why World War II manned torpedo operations tended to happen by night around new moonNew moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...
when there is the least amount of moonlight.
Open circuit scuba bubbles can make detection easy, but not easily in rough foamy sea water.
Swimming deep can hide from surface guards; but if the underwater visibility is good, he may have to go deeper than is safe with an oxygen rebreather, and with open circuit scuba he makes more bubbles at each breath in proportion to (depth + 10 meters) = (depth + 33 feet).
Infrared detection
Thermal imaging could detect a diver near or at the surface, but not so easily in warm tropical water.Millimeter wave detection
Detecting electromagnetic signals in the 27 to 200 GHzGHZ
GHZ or GHz may refer to:# Gigahertz .# Greenberger-Horne-Zeilinger state — a quantum entanglement of three particles.# Galactic Habitable Zone — the region of a galaxy that is favorable to the formation of life....
range may improve detecting surface swimmers at night, but this idea is not yet tested..
Ultrasound detection
Artificial intelligenceArtificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...
and electronic neural network
Neural network
The term neural network was traditionally used to refer to a network or circuit of biological neurons. The modern usage of the term often refers to artificial neural networks, which are composed of artificial neurons or nodes...
s and developments in ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
have made possible specialized diver-detector sonars.
Experience has showed that passive sonar (i.e. merely listening for underwater sounds) cannot detect everything; in particular it cannot easily detect rebreather divers and unequipped surface swimmers; and it can detect direction, but not distance unless readings from two or more listening stations can be correlated.
High-power low-frequency sonar commonly used for depth sounding and to detect large objects (including submarines) is not good at detecting small objects like divers, but the US Navy Diving Manual 24 says that it is hazardous to divers.
Examples of diver-detecting active sonar systems are:
- AN/WQX-2AN/WQX-2The AN/WQX-2 is a diver-detector sonar used in anti-frogman precautions. It is in service with the US Navy. It uses Kongsberg Mesotech components. It can detect divers up to 2400 feet away....
: the US Navy uses it. - AquaShield Diver Detection Sonar Designed to protect energy installations, ports and coastal facilities
- Cerberus (sonar)Cerberus (sonar)Cerberus is a blue egg-shaped ultrasound device to detect submerged divers. It is made by Qinetiq. It can distinguish a diver from a seal or dolphin or porpoise. Its range is about 700 meters = 0.435 miles. It was unveiled at UDT2003...
: a blue egg-shaped device. - CSDS-85 Omni Surveillance Sonar made by CTech
- DDS 9000 multibeam diver detection sonar: by Kongsberg GruppenKongsberg GruppenKongsberg Gruppen is Norway's major defence contractor and maritime automation supplier, located in Kongsberg, a former mining town....
- DDS-J diver-detection sonar designed to protect underwater oil pipelines: by Westminster International Ltd
- Harbour Surveillance Sonar by Marport C-Tech Ltd.
- Northstar ElectronicsNorthstar ElectronicsNorthstar Electronics Inc. is based in Newark in Nottinghamshire in England.Among other things they make underwater communications gear, and underwater diver-detection gear....
- NuvoSonicNuvoSonicIt has swimmer detection, underwater hailing by voice, and non-lethal deterrent.It uses a sonar system called Parametric Port Security Sonar System , which uses a narrow-beam sound technology called Parametric Array Sonic Echo Ranging .It claims to be able to detect divers at distances up to 2...
- UPSS = Underwater Port Security SystemUnderwater Port Security SystemThe Coast Guard unveiled the system in February 2005 at the Coast Guard Integrated Support Command in San Pedro, California.-Ship Protection System:...
- WESMAR Web System is a diver-detecter sonar.
- Sonardyne SENTINEL a new third generation diver detection sonar
- Underwater Security Systems
Trained animals
Trained dolphinDolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s and sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
s can find submerged divers. Both can see, and hear direction of sound, well underwater, and dolphins have natural sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
..
The United States Navy’s MK6 Marine Mammal System is supported by SPAWAR and uses dolphins to find and mark mines and divers in the water. This system was used in:
- Vietnam in 1970-71.
- Persian Gulf in 1987–1988.
- San Diego harbor for security during the 1996 Republican National ConventionRepublican National ConventionThe Republican National Convention is the presidential nominating convention of the Republican Party of the United States. Convened by the Republican National Committee, the stated purpose of the convocation is to nominate an official candidate in an upcoming U.S...
.
Animals, unlike remotely operated underwater vehicles (ROV), etc., need to be fed and kept fit and in training whether they are needed at work or not, and cannot be laid aside in a storeroom until needed.
This link reports that: In 1970 to 1980 trained dolphins killed 2 Russian frogmen who were putting limpet mine
Limpet mine
A limpet mine is a type of naval mine attached to a target by magnets; they are so named because of their superficial similarity to the limpet, a type of mollusk....
s on a USA cargo
Cargo
Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...
ship in Cam Ranh
Cam Ranh
Cam Ranh is a city in southern Khanh Hoa province, in the South Central Coast of Vietnam. It is the second-largest city in the province, after Nha Trang. It is located on Cam Ranh Bay. As of 2009 the city had a population of 125.311. and covers an area of 316 km².Cam Ranh becomes the second...
bay in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
. After that, Russian frogmen were trained to fight back against trained dolphins, and in an incident on the coast of Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
Russian frogmen killed trained anti-frogman dolphins.
Remote-controlled underwater vehicle
A remotely operated underwater vehicle (ROV) could search for submerged divers; but ROVs are expensive to run, and as technology is now could not attack several targets one after another as quickly as a marine mammal.Underwater ROV
An underwater ROV needs to be controlled. It could find and identify divers, and perhaps deter them. It should not be easily overpowered or attacked or outpaced by the suspect divers. If it is to attack the suspects, it should carry a suitable weapon.Surface ROV
A surface ROV can move on its own and scan below itself with sonar, but without a long-range weapon it can do little against deeply submerged suspect divers.Surveillance of civilian divers
These links http://nucnews.net/nucnews/2002nn/0206nn/020604nn.htm#555 http://commdocs.house.gov/committees/judiciary/hju88543.000/hju88543_0.HTM http://www.bookofjoe.com/2005/02/if_you_are_a_sc.html claim that after 9/11 the FBI asked the USA's largest scuba diver certification organizations to turn over the records of all divers certified since 1998; this turning-over is now done once a year.Anti-frogman weapons
Some anti-frogman weapons, and weapons that may come to mind when considering defending against frogmen, are:Attack on the surface or onshore
This is the usual method available to non-diving harbor guards, and to unofficial groups trying to restrict or prevent scuba diving in their area. For weapons, see the next section.In some circumstances, submerged open-circuit scuba divers can be followed by their bubbles until they run out of air and have to surface, and then tackled on the water surface or as they come ashore.
According to circumstances, the patrol may need some means of transporting prisoners and/or seized diving equipment away from site.
Many casual sport diving intruders may keep away on seeing visible clearly marked patrol boats and surface barriers.
Police-type or riotsquad-type non-lethal weapons
These methods may be useful when assault-boarding a boat being used by unauthorized or suspect divers, or arresting them onshore, but not often otherwise.- Mace (spray)Mace (spray)Chemical Mace is a tear gas in the form of an aerosol spray which propels a lachrymatory agent mixed with a volatile solvent. It is sometimes used as a self-defense device...
and pepper sprayPepper sprayPepper spray, also known as OC spray , OC gas, and capsicum spray, is a lachrymatory agent that is used in riot control, crowd control and personal self-defense, including defense against dogs and bears...
and teargas may make an unequipped surface swimmer drown, and are useless against a swimmer with a diving maskDiving maskA diving mask is an item of diving equipment that allows scuba divers, free-divers, and snorkelers to see clearly underwater. When the human eye is in direct contact with water as opposed to air, its normal environment, light entering the eye is refracted by a different angle and the eye is unable...
and breathing setBreathing set*Scuba set, used underwater*Rebreather, reprocesses exhaled air*Surface supplied diving, fed from the surface*Self-contained breathing apparatus, used out of water, worn by rescue workers, firefighters, and others*Spacesuit, used in space...
whether he is in or out of the water. - TaserTaserA Taser is an electroshock weapon that uses electrical current to disrupt voluntary control of muscles. Its manufacturer, Taser International, calls the effects "neuromuscular incapacitation" and the devices' mechanism "Electro-Muscular Disruption technology"...
ing a surfaced diver would either be insulated off by his rubber diving suit, or may make him panic and drown, including making him lose his scuba mouthpiece if any. Any electric-shock weapon can be shorted out by water, and also the usual design of taser's firing range underwater would be a few inches. - Bean bag roundsFlexible baton roundA bean bag round, also known by its trademarked name flexible baton round, is a baton round fired as a shotgun shell used for less lethal apprehension of suspects.-Description:...
, rubber bulletRubber bulletRubber bullets are rubber or rubber-coated projectiles that can be fired from either standard firearms or dedicated riot guns. They are intended to be a non-lethal alternative to metal projectiles...
s, pepper ballPepper ballA pepper-spray projectile, also called a pepper-spray ball, pepper-ball or pepper-spray pellet is a projectile weapon made up of a powdered chemical that irritates eyes and nose...
s, and similar would be stopped in a few inches by water. - An electric shock prod's electrodes may fail to penetrate a tough electrically insulating drysuit, or the shock delivered may be shorted out by water on a wet diving suit.
- Underwater a batonClub (weapon)A club is among the simplest of all weapons. A club is essentially a short staff, or stick, usually made of wood, and wielded as a weapon since prehistoric times....
would have to be used for thrusting or jabbing, not swung, due to water resistance; and the target's solar plexus will probably be protected by parts of his diving gear. - Police-type batonClub (weapon)A club is among the simplest of all weapons. A club is essentially a short staff, or stick, usually made of wood, and wielded as a weapon since prehistoric times....
and riotshield tactics would be of use only onshore or in a large enough boat. - JudoJudois a modern martial art and combat sport created in Japan in 1882 by Jigoro Kano. Its most prominent feature is its competitive element, where the object is to either throw or takedown one's opponent to the ground, immobilize or otherwise subdue one's opponent with a grappling maneuver, or force an...
throws and similar are unlikely to work underwater. - StunningStunningStunning is the process of rendering animals immobile or unconscious, without killing the animal, prior to their being slaughtered for food.-History:...
may be a fairly safe means of arrest on land, but underwater would likely make the diver lose his mouthpieceMouthpiece (scuba)In breathing sets, a mouthpiece is a part that the user grips in his mouth, to make a watertight seal between the breathing set and his mouth. It is composed of a short flattened-oval tube that goes in between the lips, with on its free end a flange that fits between the lips and the tooth and gums...
and drown (unless he has a fullface mask or some sorts of strapped-in mouthpiece), or lose control of depth with consequent barotraumaBarotraumaBarotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding fluid...
. - Underwater, a hand-held spearSpearA spear is a pole weapon consisting of a shaft, usually of wood, with a pointed head.The head may be simply the sharpened end of the shaft itself, as is the case with bamboo spears, or it may be made of a more durable material fastened to the shaft, such as flint, obsidian, iron, steel or...
may have some use. Otherwise, throwing rocks, or other projectileProjectileA projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
s including sharp objects, by hand is likely to work only out of water.
Shooting
Ordinary bullet-firing firearms may be useful (as a lethal weapon) against divers on the surface or men in boats or ashore, but underwater are inaccurate and very short range.Shotgun
Shotgun
A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug...
s (probably pump-action
Pump-action
A pump-action rifle or shotgun is one in which the handgrip can be pumped back and forth in order to eject a spent round of ammunition and to chamber a fresh one. It is much faster than a bolt-action and somewhat faster than a lever-action, as it does not require the trigger hand to be removed from...
, when used as a security squad weapon) may be effective when the target is out of water, but are even less useful underwater.
Special underwater firearm
Underwater firearm
An underwater firearm is a firearm specially designed for use underwater by frogmen.Underwater firearms were first conceived during the Cold War during the 1960s and 1970s as a way to arm frogmen, and remain in arms inventories today.-Design:...
s have been designed for use underwater: see #Underwater firearms below
Depth charge
A depth chargeDepth charge
A depth charge is an anti-submarine warfare weapon intended to destroy or cripple a target submarine by the shock of exploding near it. Most use explosives and a fuze set to go off at a preselected depth in the ocean. Depth charges can be dropped by either surface ships, patrol aircraft, or from...
is effective, and may be lethal, but may cause other damage underwater, and is not recommended in peacetime when the victim may be an intruding civilian sport diver, although it is alleged to have been common practice for some years after 1945 in British naval harbors.
Divers, however, are far less vulnerable to damage by underwater explosion than common sense would dictate. Since the tissues of the body tend to transmit the shock waves with much the same characteristics as the water around, large distant shocks have little impact on divers. For this reason, the most effective "depth charge" for use against a diver is the common hand-grenade, tossed within a few feet of the diver. The resulting gas cavitation and shock-front-differential over the width of the body is effective in stunning or killing the diver.
- Anti-frogman depth charge developed by RheinmetallRheinmetallRheinmetall AG is a German automotive and defence company with factories in Düsseldorf, Kassel and Unterlüß. The company has a long tradition of making guns and artillery pieces...
Microwave
The Active Denial SystemActive Denial System
The Active Denial System is a non-lethal, directed-energy weapon developed by the U.S. military. It is a strong millimeter-wave transmitter primarily used for crowd control . Some ADS such as HPEM ADS are also used to disable vehicles. Informally, the weapon is also called the heat ray...
does not work underwater, as water absorbs microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
s well (as in microwave cookers).
Magnetic field
A magnetic field generator to make the diver's navigation compassCompass
A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
misread is possible. Such a magnetic coil carried by a patrol boat directly over the target diver would affect compass readings to 5 meters (15 feet) depth at about 7 kilowatts; but to 10m (30 feet) (oxygen rebreather depth limit) at about 448 kilowatts, which is too much power need to be practical.
Sound
Requirements are different according to what sort of weapon is called for:- Lethal.
- Non-lethal, causing pain or discomfort
- Audible sound giving verbal orders.
There has been much research about the effect of sound on divers. See the bibliography
Bibliography
Bibliography , as a practice, is the academic study of books as physical, cultural objects; in this sense, it is also known as bibliology...
in nlsn (page 51 etseq, 356 entries).
Sound: summary
High intensity sound 20–100 Hz, and high intensity impulse noise, are promising as a non-lethal weapon, but more testing is needed. As a source of high-intensity 20–100 Hz sound, the sound generated by a plasma sound source is promising.The US Navy Diving Manual(page 24) says that high-power low-frequency sonar (commonly used for depth sounding and to detect large objects (including submarines)) is not good at detecting small objects like divers, but is hazardous to divers. At high enough power it could be a reliable lethal anti-diver weapon.
Ultrasound
The main effects of ultrasoundUltrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
on the human body are heating and cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
. See nlsn(pages 21–23) for detailed information. Also see ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
and sonic weaponry
Sonic weaponry
Sonic and ultrasonic weapons are weapons of various types that use sound to injure, incapacitate, or kill an opponent. Some sonic weapons are currently in limited use or in research and development by military and police forces. Others exist only in the realm of science fiction...
.
As each wave of the ultrasound passes through the diver, any bubbles in the tissue expand and contract, and the tissue heats. After a particular threshold of loudness of the ultrasound, new bubbles form during the low-pressure part and disappear during the high-pressure part: this is cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
and can cause injury.
One well-known method is a powerful blast from a ship's ordinary high-power low-frequency sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
(commonly used for depth sounding and to detect large objects (including submarines)), which deranges the diver's inner ear
Inner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
and makes him dizzy and disoriented and tends to force him to surface, or may make him panic and lose his mouthpiece and drown. These large "active sonars" are used to search for submarines and are very powerful. These sonars are usually bow mounted, and if so a diver attacking at the stern would be in the sonar baffle region and unaffected, if he gets close enough first.
Most ships, both military and non-military, carry smaller "navigation" sonars such as depth finders or collision sensors, but their high frequencies and relatively low power lack effectiveness against divers.
A test of a 230 decibel 3000 to 7000 Hz transmitter killed seven whales, causing hemorrhages around their ears: see Sonar#Sonar and marine animals - adverse effects.
Around the 1970s there were reports among sport scuba divers from offshore from a Ministry of Defence
Ministry of Defence (United Kingdom)
The Ministry of Defence is the United Kingdom government department responsible for implementation of government defence policy and is the headquarters of the British Armed Forces....
area in Dorset
Dorset
Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...
in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
of diver deaths, mass deaths of fish, and divers returning reporting "strange sonic noises": they speculated about a secret anti-frogman weapon, but it may have been merely a powerful modulated ultrasound
Modulated ultrasound
Ultrasound can be modulated to carry an audio signal . This is often used to carry messages underwater, in underwater diving communicators, and short-range communication with submarines; the received ultrasound signal is decoded into audible sound by a modulated-ultrasound receiver.-Range...
beam intended to communicate with submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s.
Some say that these speculations are mostly fanciful and that since the human body is very close to the impedance of the water around it, the ultrasound tends to pass through the body (perhaps breaking the eardrum, but not killing the diver); but if the sound or ultrasound is powerful it may cause overheating or cavitation damage on the way.
Some say that most deaths of people in the water from sonar have come from a freak combination of the diver's physical condition with local acoustic reflection of high-powered audible sonar that uncharacteristically "focused" the sound on the diver, or matched the resonant frequency of the diver's air cavities.
However:
- Early researchers into underwater ultrasound soon found that small water animals sometimes died if caught in ultrasound beams.
- This method of attack (to stun or kill) occurs in nature; it has been proved that some toothed whales can make and focus audible sound "clicks" so powerful that the whale routinely uses it to stun prey at close range. http://www.tribuneindia.com/2001/20010218/spectrum/nature.htm http://www.pc.gc.ca/pn-np/qc/mingan/natcul/natcul1a-1_E.asp
- Analysis of research literature related to effects of ultrasound concluded that reported ultrasound-caused organ damage was associated with sound pressure levels exceeding a certain intensity threshold, regardless of frequency
- The UPSS/IAS diver-detector sonarSonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
system includes an underwater shockwaveShock waveA shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
emitter: see Underwater Port Security SystemUnderwater Port Security SystemThe Coast Guard unveiled the system in February 2005 at the Coast Guard Integrated Support Command in San Pedro, California.-Ship Protection System:...
.
It is unknown what later proof or disproof there has been of speculations such as appeared in a book about Cousteau
Jacques-Yves Cousteau
Jacques-Yves Cousteau was a French naval officer, explorer, ecologist, filmmaker, innovator, scientist, photographer, author and researcher who studied the sea and all forms of life in water...
written by Philippe Diole
Philippe Diole
Philippe Victor Diole was a French author and undersea explorer.Diole was born in Saint Maur, France, son of Marcel and Elizabeth Diole. He married Marguerite Monsenergue on July 6, 1953...
around 1960, about underwater ultrasound guns making an ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
beam powerful enough to disintegrate a diver into the water except the metal parts of his kit.
To cause discomfort to the diver
A sound that irritates or causes pain. Diver aversion to low frequency
Low frequency
Low frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...
sound is dependent upon sound pressure level and center frequency
Center frequency
In electrical engineering and telecommunications, the center frequency of a filter or channel is a measure of a central frequency between the upper and lower cutoff frequencies...
.
Westminster International have also implemented this but they withhold the exact sound frequencies used: see http://www.wi-ltd.com/defence/Maritime_Defence/Acoustic_Defence_Systems/Enforcer_Underwater_CommunicationDiver_Disruption_System .
Verbal
The sound may be an order to surrender or surface or go onshore or to the patrol boat, perhaps with a threat to use non-lethal or lethal force if disobeyed. But such an order must be clear enough to be heard and understood.
Sensitivity to the sound
Underwater, human hearing is largely by bone conduction
Bone conduction
Bone conduction is the conduction of sound to the inner ear through the bones of the skull.Bone conduction is the reason why a person's voice sounds different to him/her when it is recorded and played back. Because the skull conducts lower frequencies better than air, people perceive their own...
, through the skull and not through the eardrum
Eardrum
The eardrum, or tympanic membrane, is a thin membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles...
and ossicles. This causes somewhat less acuity of hearing and a different graph of sensitivity against frequency, with a loss between 1000 Hz and 5000 Hz. This may affect ability to understand speech.
Research showed that, at depths up to at least 10m (30 feet), divers' wetsuit
Wetsuit
A wetsuit is a garment, usually made of foamed neoprene, which is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports, providing thermal insulation, abrasion resistance and buoyancy. The insulation properties depend on bubbles of gas enclosed within the material,...
hoods lessened underwater hearing sensitivity by 10 to 35 decibel
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
s at 1000 Hz and above, and by little or nothing at 250 Hz and below. With increasing depth in a hyperbaric chamber, decreases in wetsuit hood sound attenuation appear only to occur at frequencies between 500 and 1500 Hz. In the open ocean, hood attenuation at 8,000 Hz showed a significant decrease at 60 fsw and a tendency to decrease at 2,000 and 4,000 Hz compared with the 10 fsw data at the same frequencies in the chamber trials. At frequencies from 500 - 4,000 Hz wetsuit hood sound attenuation was on average 8 dB lower in the ocean than in the chamber trials.
Underwater, humans are much less able than in air to tell where a sound came from. Research showed that what ability remains is better with bang!-type noises than with pure tones.
100 to 500 Hz
Research showed that loud sound at 100 to 500 HzHertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
caused vibration, and at high powers cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
and damage.
20 to 100 Hz
Sound at 20 to 100 Hz is the resonance vibration frequency range for normal-sized adult human lungLung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s, and at high power causes discomfort from vibration in the lungs.
Loud sound in this frequency range was difficult to make, but the plasma sound source should make it easier; divers found plasma sound source noise underwater "very unpleasant".
Electric shock
A newspaper article about the Lionel CrabbLionel Crabb
Lionel "Buster" Crabb OBE, GM was a British Royal Navy frogman and MI6 diver who vanished during a reconnaissance mission around a Soviet cruiser in 1956.-Early life:...
disappearance speculated about underwater electric shock weapons mounted on warships to defend them from frogmen. This method, if it is used, imitates nature; see electric eel
Electric eel
The electric eel , is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks, of up to six hundred volts, which it uses for both hunting and self-defense. It is an apex predator in its South American range...
and electric ray
Electric ray
The electric rays are a group of rays, flattened cartilaginous fish with enlarged pectoral fins, comprising the order Torpediniformes. They are known for being capable of producing an electric discharge, ranging from as little as 8 volts up to 220 volts depending on species, used to stun prey and...
.
Mechanical devices to capture submerged divers
Such devices occur in fictionFiction
Fiction is the form of any narrative or informative work that deals, in part or in whole, with information or events that are not factual, but rather, imaginary—that is, invented by the author. Although fiction describes a major branch of literary work, it may also refer to theatrical,...
, commonly in comics. Some sorts might be possible if designed.
Small dredging-type craft and small submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s are used for small-scale dredging and/or to recover submerged objects; but there is no known case in the real world of them being used to capture divers. The craft's capture device might be a net or a grab or an aimable suction tube or a scoop.
Net
A netNet (device)
A net, in its primary meaning, comprises fibers woven in a grid-like structure, and is very infrequently mentioned in discussions of philosophy. It blocks the passage of large items, while letting small items and fluids pass...
can sometimes be used to catch submerged divers.
This agrees with talk among diving circles about a fishing trawl being the handiest way for naval men to get unwelcome or unauthorized divers out of the water.
An article at the American Academy of Underwater Sciences
American Academy of Underwater Sciences
The American Academy of Underwater Sciences is a group of Scientific organizations and individual members who conduct scientific and educational activities underwater...
1991 International Symposium
Proceedings says that the California Department of Fish and Game
California Department of Fish and Game
The California Department of Fish and Game is a department within the government of California, falling under its parent California Natural Resources Agency. The Department of Fish and Game manages and protects the state's diverse fish, wildlife, plant resources, and native habitats...
, to capture sea otter
Sea Otter
The sea otter is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg , making them the heaviest members of the weasel family, but among the smallest marine mammals...
s underwater for a relocation
Population transfer
Population transfer is the movement of a large group of people from one region to another by state policy or international authority, most frequently on the basis of ethnicity or religion...
program, successfully used a net cage apparatus front-mounted on a Dacor
Dacor (scuba diving)
Dacor is a former USA manufacturer scuba diving gear. Dacor was one of the five original United States diving gear makers: U.S. Divers, Healthways, Voit, Dacor, and Swimaster. Dacor is now merged with Mares.- External links :...
Scooter diver propulsion vehicle
Diver Propulsion Vehicle
A diver propulsion vehicle is an item of diving equipment used by scuba and rebreather divers to increase range underwater...
steered by a diver with a silent bubbleless closed circuit oxygen rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
. It is not known if a similar larger device has ever been used to capture divers underwater.
Grab
This type has been seen in fictionFiction
Fiction is the form of any narrative or informative work that deals, in part or in whole, with information or events that are not factual, but rather, imaginary—that is, invented by the author. Although fiction describes a major branch of literary work, it may also refer to theatrical,...
.
A text fiction story (The Deep Range
The Deep Range
The Deep Range is a 1957 Arthur C. Clarke science fiction novel concerning a future sub-mariner who helps farm the seas. The story includes the capture of a sea monster similar to a kraken....
by Arthur C. Clarke
Arthur C. Clarke
Sir Arthur Charles Clarke, CBE, FRAS was a British science fiction author, inventor, and futurist, famous for his short stories and novels, among them 2001: A Space Odyssey, and as a host and commentator in the British television series Mysterious World. For many years, Robert A. Heinlein,...
) mentioned a diver-catching grab
Grab
Grab may refer to:* Grab , a mechanical device* Grab , a screenshot application* Grabs * Hermann Grab , Bohemian writer of German language- Places :* Grab , Kosovo* Grab , Bosnia and Herzegovina...
used to recover a work diver suffering from nitrogen narcosis
Nitrogen narcosis
Narcosis while diving , is a reversible alteration in consciousness that occurs while scuba diving at depth. The Greek word ναρκωσις is derived from narke, "temporary decline or loss of senses and movement, numbness", a term used by Homer and Hippocrates...
, not to arrest a suspect; presumably, it is easier to rescue an impaired diver than to apprehend an unimpaired one, but it could be adapted if combined, for instance, with a stunning device.
Grab-type devices on various scales are very commonly used in nature underwater by animals. The device is usually its jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s, but in some animals evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
converted leg
Leg
Łęg may refer to the following places in Poland:*A former name for the town of Ełk *Part of the Czyżyny district of Kraków*Łęg, Pleszew County in Greater Poland Voivodeship...
s into arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...
s to handle objects; see Opabinia
Opabinia
Opabinia is an animal genus found in Cambrian fossil deposits. Its sole species, Opabinia regalis, is known from the Middle Cambrian Burgess Shale of British Columbia, Canada. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed,...
for a very early example of a nose turned into a grab.
There have been cases of unofficial groups dragging a grapnel behind a fishing boat through a group of submerged scuba divers.
Suction
A suction device might make an area suction effect in the open, or might be a suction tube extended at the frogman, who may be sucked against an opening and so held, or may be sucked inside.Such devices on a small scale are sometimes used in nature to catch prey: for example by the seahorse
Seahorse
Seahorses compose the fish genus Hippocampus within the family Syngnathidae, in order Syngnathiformes. Syngnathidae also includes the pipefishes. "Hippocampus" comes from the Ancient Greek hippos meaning "horse" and kampos meaning “sea monster”.There are nearly 50 species of seahorse...
and the pipefish
Pipefish
Pipefishes or pipe-fishes are a subfamily of small fishes, which, together with the seahorses, form the family Syngnathidae.-Anatomy:...
, and the bladderwort
Bladderwort
Utricularia, commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species . They occur in fresh water and wet soil as terrestrial or aquatic species across every continent except Antarctica...
plant. The mouths of many teleost
Teleostei
Teleostei is one of three infraclasses in class Actinopterygii, the ray-finned fishes. This diverse group, which arose in the Triassic period, includes 20,000 extant species in about 40 orders; most living fishes are members of this group...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
(for example centrarchid
Centrarchidae
The sunfishes are a family of freshwater ray-finned fish belonging to the order Perciformes. The type genus is Centrarchus . The family's 27 species includes many fishes familiar to North Americans, including the rock bass, largemouth bass, bluegill, pumpkinseed, and crappies...
s) have a strong suction component to the way they work.
Anti-swimmer barriers
Barriers can be put in the water to try to keep swimmers and frogmen out.Rigid full-depth netting
There is concern that these nets could interfere with fish migration. Due to this and expense one opinion says that they are a poor choice as frogman excluders."Safe Barrier" make
This make is metal chain-link netting placed underwater, preventing entry into an area, or at least delaying the frogmen while they cut through it.
It was made by a Swedish
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
company, Safe Barrier Systems (SBS), a division of NCC Stockholm. It is rigid metal netting, covered in polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
electrical insulation
Electrical insulation
thumb|250px|[[Coaxial Cable]] with dielectric insulator supporting a central coreThis article refers to electrical insulation. For insulation of heat, see Thermal insulation...
, and polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
abrasion protector outside that. The strands are electrified so that any frogman attack on the net will be detected by that strand going open-circuit (not to electrocute him). The grid size best suited to deter divers is 250 x 250 mm = 10 x 10 inches. Testing in the UK showed that a diver using bolt cutters could cut a hole big enough to swim through in 60–90 seconds.
It was found that the net could be evaded by climbing over it, or getting under it, or by using a wire loop to complete the circuit where he cuts each strand.
The net system can be equipped with a gate (operated by an air compressor), to allow traffic in and out of the protected area.
SBS currently supports 15 sites with "Safe Barrier" nets, including four with gates, but they are not making this net system now, due to lack of demand. The price quote for a new net was more than $7,000,000.
"F-8000" make
This make is or was made by BEI Security Systems. Its system that alarms if cut is fiber-optic.
"Aquamesh" make
This make was made by a U.K. company. It incorporated a system that set off an alarm when its fiber-optic mesh was cut. This make seems to have disappeared, and the tradename "Aquamesh" is now used for underwater wire mesh used in the aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
industry for lobster and crab traps.
Flexible full-depth netting
One effective anti-swimmer netting to date is multilayered monofilament line wide-mesh fish netting. It is almost invisible to the diver and hard to avoid. When equipped with float sensors that detect large-scale movement, these nets have proven highly effective.Sending other frogmen against them
It would seem that often a simple way of countering unknown frogmen or other divers would be for a police force or navy base personnel to send their own frogmen to investigate. This is sometimes called counter-offensive frogmen. Combat divers undergo weeks of fulltime underwater training, far more and harder than what most average civilian sport divers undergo; and they would be at full armed forces fitness even before the frogman training starts: see Frogman#Frogman training. Superior underwater combat training would likely decide which two groups of frogmen would win; generally, criminal or terrorist frogmen only have access to types of training which are available to civilians, or at least inadequate facilities.However, underwater combat between opposing teams of frogmen (although common in fiction (as in the movie Thunderball
Thunderball (film)
Thunderball is the fourth spy film in the James Bond series starring Sean Connery as the fictional MI6 agent James Bond. It is an adaptation of the novel of the same name by Ian Fleming, which in turn was based on an original screenplay by Jack Whittingham...
, and The Silent Enemy, and at least one incident in Sea Hunt
Sea Hunt
Sea Hunt was an American adventure television series that was aired in syndication by Ziv Television Programs from 1958 to 1961 and was popular in syndication for decades afterwards. The series originally aired for four seasons, with 155 episodes produced...
), and often in comics) is unusual in reality.
Sometimes diving sea-police have arrested civilian divers for illegal spearfishing
Spearfishing
Spearfishing is an ancient method of fishing that has been used throughout the world for millennia. Early civilizations were familiar with the custom of spearing fish from rivers and streams using sharpened sticks....
and diving in restricted areas and the like, and naval divers have been sent down to investigate unidentified divers in a naval harbour.
When confronted, sport divers are likelier to obey the patrol divers quietly as ordered; hostiles would be likelier to fight back.
Among the ways suggested of forcing arrested divers to surface would be attaching an inflatable float to each.
Objections to the likelihood of this tactic are:
- It may result in an underwater knife fight, risky to both sides.
- Risk of both sides drowning because of each attacking the other's breathing sets.
- This risk to the patrol divers depends on the design and resistance to damage of their equipment, e.g. kevlarKevlarKevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
-reinforced drysuit, and see Frogman#Breathing sets.- Risk of disproportionate damage to non-hostile divers by sending them to the surface too quickly, causing them to suffer a potentially lethal decompression injuryDecompression sicknessDecompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
. - It may be difficult for the patrol divers to find the suspects; but this depends on:
- Underwater visibility, which can be from a few inches to 30m (100 feet).
- The suspects using open-circuit scuba in conditions where the patrol divers can follow their exhaled bubbles.
- Light level.
- Having a hand-held sonar of the type that has a screen, e.g. the INSS, or NuvoSonicNuvoSonicIt has swimmer detection, underwater hailing by voice, and non-lethal deterrent.It uses a sonar system called Parametric Port Security Sonar System , which uses a narrow-beam sound technology called Parametric Array Sonic Echo Ranging .It claims to be able to detect divers at distances up to 2...
's diver-portable diver-detector sonar set. - A trained sea mammal leading the patrol divers to their target.
- Risk of disproportionate damage to non-hostile divers by sending them to the surface too quickly, causing them to suffer a potentially lethal decompression injury
If the patrol divers are riding suitable diver propulsion vehicle
Diver Propulsion Vehicle
A diver propulsion vehicle is an item of diving equipment used by scuba and rebreather divers to increase range underwater...
s, they could travel faster and carry better weapons (lethal or non-lethal) and equipment for sonar search and navigation and communication, and perhaps a means (e.g. grab or net) to capture suspect divers in passing and tow them alongside back to the base or patrol boat.
It was thought expensive for a team of patrol divers to be on standby all the time kitted up to dive; but France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
has police
Police
The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...
divers trained to arrest unauthorized or suspect divers underwater and to force them to surface. One common offence there is or was spearfishing
Spearfishing
Spearfishing is an ancient method of fishing that has been used throughout the world for millennia. Early civilizations were familiar with the custom of spearing fish from rivers and streams using sharpened sticks....
while using breathing apparatus.
See Frogman#Equipment for features useful in equipment of frogmen who may get into underwater fights.
The Russian PDSS
Russian commando frogmen
# Scout diver is a Russian term for members of a special purpose unit of the Russian or Soviet Naval Spetsnaz - SpN VMF .# Сombat swimmer is a Russian term meaning members of special purpose anti-sabotage divers' units...
system is an example of an anti-frogman defence system which includes frogmen trained in underwater fights.
See Russian commando frogmen
Russian commando frogmen
# Scout diver is a Russian term for members of a special purpose unit of the Russian or Soviet Naval Spetsnaz - SpN VMF .# Сombat swimmer is a Russian term meaning members of special purpose anti-sabotage divers' units...
under "1970 and after" for a report of a real underwater fight between a guard squad of Russian PDSS frogmen and intruding enemy frogmen.
The films Above Us the Waves and The Silent Enemy are reconstructions of real World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
events, and each shows an underwater fight between opposing groups of frogmen, but those fights did not happen in the real events.
Underwater firearms
Some navies have thought underwater fights to be likely enough for them to design underwater firearmUnderwater firearm
An underwater firearm is a firearm specially designed for use underwater by frogmen.Underwater firearms were first conceived during the Cold War during the 1960s and 1970s as a way to arm frogmen, and remain in arms inventories today.-Design:...
s for frogmen to use as a lethal weapon; there is said to have been a real incident when Russian frogmen shot two anti-frogman dolphins.
These underwater firearms fire a steel rod, not a bullet, for better range underwater. They are all more powerful than a speargun
Speargun
A speargun is an underwater fishing implement designed to fire a spear at fish.The basic components of a speargun are:A spear, a stock/barrel, and a handle/grip containing a trigger mechanism...
, and can fire several shots before reloading. Their barrels are not rifled
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
; the fired projectile is kept in line underwater by hydrodynamic effects, and is somewhat inaccurate when fired out of water.
The rifles are more powerful than the pistols (and look more impressive in frogmen's group photographs), but the pistols are more easily swung sideways quickly underwater at a target.
Other underwater man-carried weapons
- For a long time the diver's standard weapon and tool has been a heavy knifeKnifeA knife is a cutting tool with an exposed cutting edge or blade, hand-held or otherwise, with or without a handle. Knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools...
. - A catalog issued in 1991 by Life Support Engineering (now Mercury Products) contained several militaryMilitaryA military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
/ commandoCommandoIn English, the term commando means a specific kind of individual soldier or military unit. In contemporary usage, commando usually means elite light infantry and/or special operations forces units, specializing in amphibious landings, parachuting, rappelling and similar techniques, to conduct and...
type diving kit items and also a compressed-air powered speargunSpeargunA speargun is an underwater fishing implement designed to fire a spear at fish.The basic components of a speargun are:A spear, a stock/barrel, and a handle/grip containing a trigger mechanism...
. - Underwater, a batonClub (weapon)A club is among the simplest of all weapons. A club is essentially a short staff, or stick, usually made of wood, and wielded as a weapon since prehistoric times....
would have to be used for thrusting or jabbing, not swung, due to water resistance, and designed accordingly; and the target's solar plexus will probably be protected by parts of his diving gear.
Trained animals, as weapons
A reported anti-frogman guard is (or was) dolphinDolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s trained to carry on the nose a device which injects a large amount of compressed carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
into the frogman. This would likely be lethal due to blood embolism
Embolism
In medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...
. It is said that they were trained at Point Mugu. It was said that this device was abandoned because of fears that wild dolphins might imitate and start harassing ordinary divers. Today the mammals are primarily trained to force the diver to the surface using pushing techniques in the assumption that the majority of incursions can be addressed in this manner.
This link says that the US Navy has deployed sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
s to detect divers
Underwater diving
Underwater diving is the practice of going underwater, either with breathing apparatus or by breath-holding .Recreational diving is a popular activity...
in the Persian Gulf
Persian Gulf
The Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
. The sea lion is trained to detect the diver, connect a marker buoy
Marker buoy
Marker buoy may refer to:* Surface Marker Buoy used by divers* a light-emitting or smoke-emitting buoy used in naval warfare...
to his leg by a C-shaped handcuff-like clamp, surface, and then bark loudly to raise the alarm. 20 sea lions have been trained for this at the US Naval Warfare Systems Center in San Diego. Some have been flown to Bahrain
Bahrain
' , officially the Kingdom of Bahrain , is a small island state near the western shores of the Persian Gulf. It is ruled by the Al Khalifa royal family. The population in 2010 stood at 1,214,705, including 235,108 non-nationals. Formerly an emirate, Bahrain was declared a kingdom in 2002.Bahrain is...
to help the Harbor Patrol Unit to guard the US Navy's 5th Fleet. Sea lions adapt easily to warm water, can dive repeatedly and swim up to 25 mph, can see in near-darkness, and can tell where sound comes from underwater. In training the sea lions have been known to chase divers onto land. See also this link.
This link reports that in 1970 to 1980 trained dolphins killed 2 Russian frogmen who were putting limpet mine
Limpet mine
A limpet mine is a type of naval mine attached to a target by magnets; they are so named because of their superficial similarity to the limpet, a type of mollusk....
s on a USA cargo
Cargo
Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...
ship in Cam Ranh
Cam Ranh
Cam Ranh is a city in southern Khanh Hoa province, in the South Central Coast of Vietnam. It is the second-largest city in the province, after Nha Trang. It is located on Cam Ranh Bay. As of 2009 the city had a population of 125.311. and covers an area of 316 km².Cam Ranh becomes the second...
bay in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
. After that, Russian PDSS frogmen were trained to fight back against trained dolphins, and in an incident on the coast of Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
PDSS frogmen killed trained anti-frogman dolphins. Arrival of underwater rifles and pistols seems to make the trained animal threat less.
Animals, unlike ROV
Rov
Rov is a Talmudic concept which means the majority.It is based on the passage in Exodus 23;2: "after the majority to wrest" , which in Rabbinic interpretation means, that you shall accept things as the majority....
s etc., need to be fed and kept in training whether they are needed at work or not, and cannot be laid aside in a storeroom until needed.
Remote-controlled underwater vehicle, as weapon
A ROVRov
Rov is a Talmudic concept which means the majority.It is based on the passage in Exodus 23;2: "after the majority to wrest" , which in Rabbinic interpretation means, that you shall accept things as the majority....
, as well as searching, could be equipped to arrest or attack divers on command, but with their technology as it is could not attack several targets one after another as quickly as a marine mammal. A surface-only ROV would need a long-range weapon to be effective against deeply submerged suspect divers.
Preventing public access to frogman-type diving gear, or to any diving gear
- Siebe GormanSiebe GormanSiebe Gorman & Company Ltd was a British company which developed diving equipment and breathing equipment and worked on commercial diving and marine salvage projects...
had a policy in Great Britain until around 1956 of keeping prices of aqualungsAqua-lungAqua-Lung was the original name of the first open-circuit free-swimming underwater breathing set in reaching worldwide popularity and commercial success...
too high for most civilians to afford; legal restrictions on exporting currencyCurrencyIn economics, currency refers to a generally accepted medium of exchange. These are usually the coins and banknotes of a particular government, which comprise the physical aspects of a nation's money supply...
stopped people from importing cheaper foreign aqualungs. See Timeline of underwater technology#Public interest in scuba diving takes off for how this barrier broke down, starting with British sport divers making their own aqualungs from ex-RAF cylinders and converted Calor gas regulators. - The SubskimmerSubskimmerThe Subskimmer is a Diver Propulsion Vehicle which is a form of RIB with an outboard petrol engine. It is equipped to inflate and deflate itself as it runs. When submerged it seals its motor and runs with battery-electric thrusters, which are on a rotatable cross-arm, and is deflated...
, which is useful for covert underwater penetration, took decades to develop and passed through at least three firms and is still too expensive for sport divers and sport diving centers. This may be due to interference from MinistriesMinistry (government department)A ministry is a specialised organisation responsible for a sector of government public administration, sometimes led by a minister or a senior public servant, that can have responsibility for one or more departments, agencies, bureaus, commissions or other smaller executive, advisory, managerial or...
. Or it could have been a commercial decision: the market for sports use was judged to be too small. - Siebe GormanSiebe GormanSiebe Gorman & Company Ltd was a British company which developed diving equipment and breathing equipment and worked on commercial diving and marine salvage projects...
consistently refused to sell rebreathers to the civilian public. Mixture rebreatherRebreatherA rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
development was kept away from the public eye and the sport scuba trade until the end of the Cold WarCold WarThe Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
in 1991. As a result, when North Sea OilNorth Sea oilNorth Sea oil is a mixture of hydrocarbons, comprising liquid oil and natural gas, produced from oil reservoirs beneath the North Sea.In the oil industry, the term "North Sea" often includes areas such as the Norwegian Sea and the area known as "West of Shetland", "the Atlantic Frontier" or "the...
exploration started in the 1960s, the oil drilling firms needing deep-dive work had to develop nitrox diving techniques independently, from concept up, without using the Royal NavyRoyal NavyThe Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
's know-how; and then the Navy revealed that they had used nitrox diving (which the Navy called "mixture") before 1945. - In the U.S., military rebreatherRebreatherA rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
s were not marketed to the public primarily due to cost and attendant legal liabilityLegal liabilityLegal liability is the legal bound obligation to pay debts.* In law a person is said to be legally liable when they are financially and legally responsible for something. Legal liability concerns both civil law and criminal law. See Strict liability. Under English law, with the passing of the Theft...
issues. Legal issues still tend to discourage the development and sale of the rebreather in the U.S., though acceptance and use is growing. The U.S. military has not tried to stop sales of rebreathers to the public in the U.S., as it has realized that recreational SCUBA has now exceeded earlier military SCUBA in quality, and hopes that a similar increase in quality and decrease in price will come from commercial-off-the-shelf rebreather equipment.
Prevention technology
New technology now exists where underwater speaker systems can be deployed around the designated area(s). This array of speaker systems can be programmed to send high powered frequencies which then blasts powerful ‘disruption’ signals into the water. The frequencies have a maximum disorientation effect on the diver(s), which induce discomfort or panic causing them to leave the area or surface for interception. In cases where the divers remain in the water, the frequencies are likely to have a continued adverse effect which could cause sickness and confusion.Preventing public access to diving water
For sport divers and similar who have no means of covert entry, one method is merely to try to stop all divers from reaching water, or stopping them from using boats, in some particular place or area. Such a bylawBylaw
By-law can refer to a law of local or limited application passed under the authority of a higher law specifying what things may be regulated by the by-law...
may be called for by the military to keep sport divers away from secret underwater sites, or by inshore fishermen to stop alleged poaching of shellfish
Shellfish
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
.
The U.S. has made many such regulations to protect such infrastructure
Infrastructure
Infrastructure is basic physical and organizational structures needed for the operation of a society or enterprise, or the services and facilities necessary for an economy to function...
s as power plant and nuclear plant water intakes and discharges, bridge foundations, harbor and pier installations, and naval facilities.
The Socialist Federal Republic of Yugoslavia
Socialist Federal Republic of Yugoslavia
The Socialist Federal Republic of Yugoslavia was the Yugoslav state that existed from the abolition of the Yugoslav monarchy until it was dissolved in 1992 amid the Yugoslav Wars. It was a socialist state and a federation made up of six socialist republics: Bosnia and Herzegovina, Croatia,...
(until it broke up) forbade all sport diving except a few Government-controlled groups, and required official permission for each campaign of archaeological or scientific diving.
Contents guide to ref. 2
Ref. [2] is http://www.spawar.navy.mil/sti/publications/pubs/td/3138/td3138cond.pdf, released by Waterfront Physical Security, about 3 megabytes, PDF format, 82 pages, has images. Contents:| sec | page | title | summary & references |
|---|---|---|---|
| ii | Administrative information | "This document is not copyright Copyright Copyright is a legal concept, enacted by most governments, giving the creator of an original work exclusive rights to it, usually for a limited time... ed", etc. |
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| iii | Executive summary | ||
| 1 | 1 | The need for a non-lethal response | to diver intrusion was highlighted by the USS Cole bombing USS Cole bombing The USS Cole Bombing, or the USS Cole Incident, was a suicide attack against the United States Navy destroyer on October 12, 2000 while it was harbored and refueled in the Yemeni port of Aden. Seventeen American sailors were killed, and 39 were injured... . |
| 2 | 3 | Detection | Active sonar Sonar Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels... is needed, as passive sonar is not fully effective. And see #Detection. |
| 3 | About the US Navy's AN/WQX-2 swimmer-detection sonar, with images. | ||
| 3 | 7 | Search parameters | Which devices are suitable?, since many intruders will be innocent sport divers. |
| 4 | 9 | Existing in-air approaches | About various anti-riot and similar devices which are routinely used on land. |
| 4.1 | 9 | Projectiles | Bean bag Flexible baton round A bean bag round, also known by its trademarked name flexible baton round, is a baton round fired as a shotgun shell used for less lethal apprehension of suspects.-Description:... rounds, rubber bullet Rubber bullet Rubber bullets are rubber or rubber-coated projectiles that can be fired from either standard firearms or dedicated riot guns. They are intended to be a non-lethal alternative to metal projectiles... s, pepper ball Pepper ball A pepper-spray projectile, also called a pepper-spray ball, pepper-ball or pepper-spray pellet is a projectile weapon made up of a powdered chemical that irritates eyes and nose... s, & similar are not suitable. |
| 4.2 | 9 | Chemical agents and electrical devices | Mace Mace (spray) Chemical Mace is a tear gas in the form of an aerosol spray which propels a lachrymatory agent mixed with a volatile solvent. It is sometimes used as a self-defense device... & pepper spray Pepper spray Pepper spray, also known as OC spray , OC gas, and capsicum spray, is a lachrymatory agent that is used in riot control, crowd control and personal self-defense, including defense against dogs and bears... may drown surface swimmer and are useless against man with breathing set Scuba set A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving. It is much used for sport diving and some sorts of work diving.... . |
| 10 | Taser Taser A Taser is an electroshock weapon that uses electrical current to disrupt voluntary control of muscles. Its manufacturer, Taser International, calls the effects "neuromuscular incapacitation" and the devices' mechanism "Electro-Muscular Disruption technology"... s are not suitable except perhaps on surface within 5m (15 feet) of the boat, & then risky. |
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| 4.3 | 10 | Physical force | by patrol divers; and see #Sending other frogmen against them. |
| 11 | by trained dolphins or sealions; and see #Trained animals. | ||
| 12 | Sending an ROV Rov Rov is a Talmudic concept which means the majority.It is based on the passage in Exodus 23;2: "after the majority to wrest" , which in Rabbinic interpretation means, that you shall accept things as the majority.... down to look for the suspect divers. |
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| 4.4 | 14 | Restraints | Net barriers; and see #Anti-swimmer netting. |
| 5 | 17 | Light- and sound-producing devices | |
| 5.1 | 17 | Light-producing devices | intended to dazzle Glare (vision) Glare is difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions.... . May cause epilepsy Epilepsy Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases... . Less use under water. |
| 5.2 | 18 | Sound-producing devices | A table |
| 5.2.1 | 19 | Acoustics terminology | An equation and a table |
| 5.2.2 | 20 | Which bioeffect? | Which effect on the suspect diver's body to aim for?; a table & science |
| 5.2.3 | 21 | Ultrasound Ultrasound Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is... |
And see #Ultrasound weapon & Sonic weaponry#Lethal sonic weapons, underwater. |
| 5.2.4 | 23 | Infrasound Infrasound Infrasound is sound that is lower in frequency than 20 Hz or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high... (1–20 Hz) |
No definite result yet; probably no use. |
| 5.2.5 | 25 | Audible sound | And see #Audible sound: irritating, or painful, or verbal orders. |
| 5.2.5.1 | 26 | Diver hearing | About divers' ability to hear underwater. A graph. |
| 5.2.5.2 | 26 | Fetal studies | Effect on fetus Fetus A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The... es. |
| 5.2.5.3 | 29 | Hearing-related bioeffects | Research on making noises irritating. |
| 5.2.5.4 | 30 | Acoustic deterrent devices used by fish farms | to keep seal Pinniped Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped... s away. |
| 5.2.5.5 | 31 | Extra-aural bioeffects | Effect of audible sound other than on the ears. |
| 5.2.5.5.1 | 32 | Low frequency (100–500 Hz) | Long description of research results. |
| 5.2.5.5.2 | 35 | Extra-aural bioeffects in humans | Including results of experiments on submerged divers. |
| 5.2.5.5.3 | 37 | Very low frequency (20–100 Hz) | Description of research results. |
| 5.2.5.6 | 40 | Impulse noise (startle response) | Research results |
| 5.2.5.6.1 | 42 | Plasma sound source | Noise from an underwater spark gap. Not a magic frequency like Star Trek Star Trek Star Trek is an American science fiction entertainment franchise created by Gene Roddenberry. The core of Star Trek is its six television series: The Original Series, The Animated Series, The Next Generation, Deep Space Nine, Voyager, and Enterprise... "phaser on stun", but it seems promising. |
| 6 | 45 | Electromagnetic Electromagnetism Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation... devices |
The Active Denial System Active Denial System The Active Denial System is a non-lethal, directed-energy weapon developed by the U.S. military. It is a strong millimeter-wave transmitter primarily used for crowd control . Some ADS such as HPEM ADS are also used to disable vehicles. Informally, the weapon is also called the heat ray... does not work underwater. Magnetic field generator to make a suspect diver's compass Compass A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined... misread is considered. |
| 7 | 47 | Towards a non-lethal swimmer deterrent device | High intensity sound 20–100 Hz, & high intensity impulse noise, are promising. More testing is recommended. |
| 8 | 49 | Summary | Recommends: Visible patrol boats & barriers to deter sport divers & similar. Audio commands to submerged divers. 20–100 Hz sound as a severe irritant. |
| 9 | 51 | Bibliography | has 356 entries. |
- For other documents by the same organization (SSC San Diego), see Technical Reports and Documents.