A naval drifter is a boat built along the lines of a commercial fishing drifter

Drifter (fishing boat)

A drifter is a type of fishing boat. They were designed to catch herrings in a long drift net. Herring fishing using drifters has a long history in the Netherlands and in many British fishing ports, particularly in East Scottish ports....

 but fitted out for naval purposes. The use of naval drifters is paralleled by the use of naval trawler

Naval trawler

A naval trawler is a vessel built along the lines of a fishing trawler but fitted out for naval purposes. Naval trawlers were widely used during the First and Second world wars. Fishing trawlers were particularly suited for many naval requirements because they were robust boats designed to work...

s.

Fishing trawlers were designed to tow heavy trawls, so they were easily adapted to tow minesweepers, with the crew and layout already suited to the task. Drifters were robust boats built, like trawlers, to work in most weather conditions, but designed to deploy and retrieve drift net

Drift net

Drift netting is a fishing technique where nets, called drift nets, are allowed to float freely at the surface of a sea or lake. Usually a drift net is a gill net with floats attached to a rope along the top of the net, and weights attached to another rope along the foot of the net to keep the net...

s. They were generally smaller and slower than trawlers. If requisitioned by navies, they were typically armed with an anti-submarine gun and depth charges and used to maintain and patrol anti-submarine nets.

World War I

Like fishing trawlers, the Royal Navy

Royal Navy

The 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...

 requisitioned many fishing drifters for conversion to naval use during World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

.

In addition, 362 naval drifters were ordered to Admiralty

Admiralty

The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...

 specifications (and thus are often referred to as "Admiralty drifters"). Shipyards used to building fishing trawlers or drifters could easily switch to constructing naval versions. As a bonus these drifters could be sold to commercial fishing interests when the war ended.

There were two basic types of Admiralty built drifter, wooden hull and steel hull.

• The wooden hull vessels displaced 175 tons, were 86 ft (26.2 m) long, with a beam of 19 ft (5.8 m). They had a speed of 9 knots and carried one 6pdr gun. 91 wooden hull vessels were launched 1918–20, and 100 similar Canadian-built craft were ordered in January 1917.

• The steel hull vessels displaced 199 tons, were 86 ft (26.2 m) long, with a beam of 18 ft 6in (5.6 m). They also had a speed of 9 knots and carried one 6pdr gun. 123 steel-hulled vessels were launched 1917–1920, and 48 others were cancelled.

Royal Navy drifters were named like the trawlers were, except for the Canadian-built vessels which were numbered CD 1 to CD 100.

During 1917, a fleet of British drifters, escorted by destroyers and light cruisers, maintained a blockade of the 100 km (62.1 mi) wide Otranto Straits, denying the Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

 access to the Mediterranean. On 15 May 1917, the Austro-Hungarian Navy raided the barrage

Battle of the Strait of Otranto (1917)

The 1917 Battle of the Strait of Otranto was the result of an Austro-Hungarian raid on the Otranto Barrage, an Allied naval blockade of the Strait of Otranto. The battle took place on 14–15 May 1917, and was the largest surface action in the Adriatic Sea during World War I...

. The Austro-Hungarians gave most drifter crews warning to abandon ship before opening fire. Some drifter crews chose to fight, and the Gowan Lee returned fire on the Austro-Hungarian ships. The drifter was heavily damaged, but remained afloat. Skipper Joseph Watt

Joseph Watt

Joseph Watt, VC was a Scottish recipient of the Victoria Cross, the highest and most prestigious award for gallantry in the face of the enemy that can be awarded to British and Commonwealth forces...

 was later awarded the Victoria Cross

Victoria Cross

The Victoria Cross is the highest military decoration awarded for valour "in the face of the enemy" to members of the armed forces of various Commonwealth countries, and previous British Empire territories....

for his actions during the battle. Of the 47 drifters in the barrage at the time, 14 were sunk and 4 were damaged. The lack of sufficient Allied escorts forced the withdrawal of the remaining blockading ships, although only for a short time.