HMS Seahorse (98S)

Seahorse on the surface
History
United Kingdom
Name	Seahorse
Ordered	16 March 1931
Builder	Chatham Dockyard
Laid down	14 September 1931
Launched	15 November 1932
Completed	2 October 1933
Identification	Pennant number: 98S
Fate	Sunk, 7 January 1940
Badge
General characteristics
Class and type	S-class submarine
Displacement	730 long tons (740 t) surfaced 927 long tons (942 t) submerged
Length	202 ft 6 in (61.7 m)
Beam	24 ft (7.3 m)
Draught	11 ft 11 in (3.6 m)
Installed power	1,550 bhp (1,160 kW) (diesel) 1,300 hp (970 kW) (electric)
Propulsion	2 × diesel engines 2 × electric motors
Speed	13.75 knots (25.47 km/h; 15.82 mph) surfaced 10 knots (19 km/h; 12 mph) submerged
Range	3,700 nmi (6,900 km; 4,300 mi) at 10 knots (19 km/h; 12 mph) surface; 64 nmi (119 km; 74 mi) at 2 knots (3.7 km/h; 2.3 mph) submerged
Test depth	300 feet (91.4 m)
Complement	38
Armament	6 × bow 21 in (533 mm) torpedo tubes 1 × 3-inch (76 mm) deck gun

HMS Seahorse was a first-batch S-class submarine (often called the Swordfish class) built for the Royal Navy during the 1930s. Ordered in March 1931, she was laid down at Chatham Dockyard in September 1931 and launched on 15 November 1932.

At the start of World War II, Seahorse was conducting a patrol southwest of Stavanger, Norway. While returning to port after her first and uneventful patrol, Seahorse was erroneously attacked with depth charges by a British aircraft. After repairs, she conducted a second war patrol, sighting the surfaced submarine U-36 on 13 November 1939. Her torpedoes missed their target, however. During her next patrol on 30 October, Seahorse sighted another German submarine, U-21, but it submerged before torpedoes could be launched. On 18 November, Seahorse spotted two German ships, very probably the destroyers Z21 Wilhelm Heidkamp and Z19 Hermann Künne, but failed to maneuver into an attack position. On 26 December, Seahorse departed for her sixth and last war patrol, off Heligoland Bight, with orders to patrol off Heligoland then shift to the mouth of the Elbe on 30 December, then return to port on 9 January 1940, but she did not return on her due date. It was originally thought that she had struck a mine, but German records, examined after the war, suggest she was sunk by the German First Minesweeper Flotilla, which reported an attack on an unidentified submarine on 7 January 1940. It is, however, also possible that she was rammed and sunk by the German Sperrbrecher IV/Oakland southeast of Heligoland on 29 December 1939.