The Acheron class was a repeat of the preceding Acorn class. The Admiralty provided general specifications, but each shipyard did their own detailed design so that ships often varied in size.[2] The Acherons had an overall length of 246 feet (75 m), a beam of 23 feet 8 inches (7.2 m), and a draught of 8 feet 9 inches (2.7 m). The ships displaced 778 long tons (790 t) at deep load and their crew numbered 70 officers and ratings.[3]
Hydra was powered by a single Brown-Curtis steam turbine that drove both propeller shafts using steam provided by three Yarrow boilers. The engines developed a total of 13,500 shaft horsepower (10,100 kW) and were designed for a speed of 27 knots (50 km/h; 31 mph). The ship reached a speed of 28.1 knots (52.0 km/h; 32.3 mph) from 14,710 shp (10,970 kW) during her sea trials.[4] The Acherons had a range of 1,620 nautical miles (3,000 km; 1,860 mi) at a cruising speed of 15 knots (28 km/h; 17 mph).[3]
She was present at the Battle of Jutland[8] on 31 May 1916. Along with the rest of the flotilla, she was transferred to the 3rd Battle Squadron, based at Portsmouth.[9]
She collided with a merchant ship on the night of 11 February 1917 in the English Channel. The captain of Hydra was held liable for the collision because, although the other ship showed him a light, he did not perceive that it was on a crossing course.[10]
Mediterranean service
From 1917 the Third Battle Squadron was deployed to the Mediterranean. Hydra was present at the entry of the Allied Fleet through the Dardanelles on 12 November 1918.[11] On 9 February 1921, Hydra collided with the Royal Navy torpedo boatZ 3 in the Weilingen Channel and sank. Z 3 rescued all 72 of Hydra′s crew.[12] The ship was sold on 9 May 1921 to Thos. W. Ward of Portishead for scrap.[13]