Although small by naval standards, it was larger than the preceding Coastal Motor Boats of 40 and 55 ft length. The first motor launches entered service in the First World War. These were 580 80-foot-long (24 m) vessels built by the US Elco company for the Admiralty, receiving the designations ML-1 to ML-580. They served between 1916 and the end of the war with the Royal Navy defending the British coast from German submarines. Some of the earliest examples, including ML 1, also served in the Persian Gulf from June 1916 onwards. After the Armistice of 11 November 1918 a flotilla of 12 RN Motor Launches traveled down the Rhine performing duty as the Rhine Patrol Flotilla.
|Fairmile A motor launch||110 ft||57 tons||25 knots (46 km/h)||1939||12||Submarine chasing, later minelaying|
|Fairmile B motor launch||112 ft (34 m)||85 tons||20 knots (37 km/h)||1940-45||1,284||Submarine chasing, many later roles including air-sea rescue|
|Harbour defence motor launch||72 ft (22 m)||54 tons||12 knots (22 km/h)||1940-45||486||47||Defending harbours; anti-submarine|
|RAF Type 2 Whaleback||63 ft (19 m)||21.5 tons||36 knots (67 km/h)||1940-42||70||Rescuing downed aircrew, particularly in the English Channel|