A naval drifter is a boat built along the lines of a commercial fishing drifter but fitted out for naval purposes. The use of naval drifters is paralleled by the use of naval trawlers.
British drifters sailing from their base in the Adriatic to the Otranto Barrage
The Canadian CD-class naval drifter, CD 27, built during World War I for the Royal Canadian Navy. Many became fishing vessels after the war.
A Great Yarmouth drifter George Albert during the war
Naval trawlers are vessels built along the lines of a fishing trawler but fitted out for naval purposes; they were widely used during the First and Second World Wars. Some, known in the Royal Navy as
First World War naval trawler, HMT Swansea Castle
Second World War naval trawler, HMT Lancer
A naval trawler's gun crew mans a 12-pounder (76 mm) Mk V gun on the forecastle
HMT Northern Sky pitching and rolling at slow speed along her patrol lines. Operating off Iceland, this trawler made the last attack of the Second World War on a U-boat.