Distance line
Encyclopedia
A distance line, penetration line or guideline is an item of diving equipment
used by SCUBA divers
as a means of returning to a safe starting point in conditions of low visibility, water currents or where pilotage
is difficult. They are often used in cave diving
and wreck diving
where the diver must return to open water after a penetration when it may be difficult to discern the return route. Guidelines are also useful in the event of silt out
.
Distance lines are often wound on to a spool or a reel
. Then length of the distance line used is proportional to the length needed for the dive. An open water diver using the distance line only for a surface marker buoy
may only need 50 metres / 165 feet, whereas a cave diver will use multiple reels of lengths from 50 ft to 1000+ ft. Reels for distance lines usually have a locking mechanism to control deployment of the line and a winding handle to help keep slack line under control. Lines are used in open water to deploy surface marker buoy
s and decompression buoys and link the buoy on the surface to the submerged diver.
The material of line used on any given distance line will vary based on intended use. A common line used is 2mm / 0.08 inch polypropylene
line.
The use of guideline for navigation careful attention to line following, referencing, positioning, teamwork, and communication.
published Basic Cave Diving: A Blueprint for Survival which pointed out that the lack of a continuous guideline was one of five contributing factors in cave diving
accidents.
Diving equipment
Diving equipment is equipment used by underwater divers for the purpose of facilitating diving activities. This may be equipment primarily intended for this purpose, or equipment intended for other puprposes which is found to be suitable for diving use....
used by SCUBA divers
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
as a means of returning to a safe starting point in conditions of low visibility, water currents or where pilotage
Pilotage
Pilotage is the use of fixed visual references on the ground or sea by means of sight or radar to guide oneself to a destination, sometimes with the help of a map or nautical chart. People use pilotage for activities such as guiding vessels and aircraft, hiking and Scuba diving...
is difficult. They are often used in cave diving
Cave diving
Cave diving is a type of technical diving in which specialized equipment is used to enable the exploration of caves which are at least partially filled with water. In the United Kingdom it is an extension of the more common sport of caving, and in the United States an extension of the more common...
and wreck diving
Wreck diving
Wreck diving is a type of recreational diving where shipwrecks are explored. Although most wreck dive sites are at shipwrecks, there is an increasing trend to scuttle retired ships to create artificial reef sites...
where the diver must return to open water after a penetration when it may be difficult to discern the return route. Guidelines are also useful in the event of silt out
Silt out
A silt out is a situation when underwater visibility is rapidly reduced to zero.It often happens from divers' swimfins disturbing silt, particularly in caves or in still fresh water....
.
Reel
A reel is an object around which lengths of another material are wound for storage. Generally a reel has a cylindrical core and walls on the sides to retain the material wound around the core...
. Then length of the distance line used is proportional to the length needed for the dive. An open water diver using the distance line only for a surface marker buoy
Surface Marker Buoy
A surface marker buoy, SMB or simply a blob is an inflatable buoy used by scuba divers, with a line, to indicate the diver's position to their surface safety boat while the diver is underwater.- Standard buoy :...
may only need 50 metres / 165 feet, whereas a cave diver will use multiple reels of lengths from 50 ft to 1000+ ft. Reels for distance lines usually have a locking mechanism to control deployment of the line and a winding handle to help keep slack line under control. Lines are used in open water to deploy surface marker buoy
Surface Marker Buoy
A surface marker buoy, SMB or simply a blob is an inflatable buoy used by scuba divers, with a line, to indicate the diver's position to their surface safety boat while the diver is underwater.- Standard buoy :...
s and decompression buoys and link the buoy on the surface to the submerged diver.
The material of line used on any given distance line will vary based on intended use. A common line used is 2mm / 0.08 inch polypropylene
Polypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
line.
The use of guideline for navigation careful attention to line following, referencing, positioning, teamwork, and communication.
History
In 1977, Sheck ExleySheck Exley
-Biography:Exley is widely regarded as one of the pioneers of cave diving, writing two major books on the subject: Basic Cave Diving: A Blueprint for Survival and Caverns Measureless to Man published by Cave Books, , and establishing many of the basic safety procedures used in cave and overhead...
published Basic Cave Diving: A Blueprint for Survival which pointed out that the lack of a continuous guideline was one of five contributing factors in cave diving
Cave diving
Cave diving is a type of technical diving in which specialized equipment is used to enable the exploration of caves which are at least partially filled with water. In the United Kingdom it is an extension of the more common sport of caving, and in the United States an extension of the more common...
accidents.