HMS Squirrel was built for the Royal Navy as a coast guard vessel, commissioned in 1905 to replace the previous HMS Squirrel. She was built at Belfast by Workman, Clark and Company as yard number 215, launched on 21 December 1904 and completed early in 1905. The displacement of Squirrel was 230 t (250 short tons), her dimensions 103 ft (31 m) length overall and 21 ft (6.4 m) beam, and she was fitted with a 300 ihp steam engine giving her a speed of 10 knots. She was armed with two 3-pounder guns.