HMS Seahorse (98S): Lost Somewhere Off Heligoland

Built at Chatham Between the Wars

HMS Seahorse was built at Chatham Dockyard, laid down in September 1931, launched in November 1932 and commissioned in October 1933, one of the First Group of the Royal Navy's S-class submarines.

Her prewar service included a collision with the destroyer HMS Foxhound in September 1938, and once war broke out in September 1939 she sailed almost immediately on her first patrol off Stavanger, Norway, an early test of a boat that had already had a few scrapes before the shooting started.

A Dangerous Beginning to the War

Seahorse's first weeks of war proved remarkably eventful. On 5 September 1939, barely a fortnight into the conflict, she was mistakenly attacked and depth charged by a British Anson aircraft while returning from patrol, damaging her sonar equipment, a stark early reminder of how easily friendly forces could mistake a submarine for the enemy.

Later that month she fired torpedoes at the German submarine U-36 without success, and in October narrowly missed the chance to engage another U-boat she had sighted but could not close on. By December she had transferred to the 6th Submarine Flotilla, based at Blyth, under the command of Lieutenant Dennis Massy-Dawson.

Lost With All Hands

HMS Seahorse sailed from Blyth on her final patrol on 26 December 1939 and never returned. What actually happened to her remains properly disputed even today, and this history will not pretend otherwise.

The account long accepted by the Admiralty holds that she was attacked and depth charged by a German minesweeping vessel on 7 January 1940 north west of Heligoland, though even the most detailed contemporary naval records hedge on this conclusion, noting she may equally have struck a mine.

More recent research by specialist naval historians, drawing on a detailed 1980s Admiralty review, has instead argued that Seahorse most likely struck a mine several days earlier still, on the night of 29 to 30 December 1939, while transiting directly through a heavily mined stretch of the North Sea on her way to her assigned patrol area, and that the widely cited depth charge attack on 7 January may in fact have been against an entirely different, unidentified contact.

This is a genuine and unresolved historical question, and deserves to be presented honestly as such rather than settled with false confidence.

A Crew Remembered, Not Precisely Counted

Every member of Seahorse's crew was lost, a devastating blow so early in the war, though even the exact number of men aboard is recorded inconsistently across otherwise reliable sources, with figures ranging from thirty eight to thirty nine and, in one detailed named account, as high as forty six.

Whatever the precise figure, this was a complete and total loss of life that deserves to be remembered with the fullest seriousness, a submarine and her entire company gone within weeks of the war beginning, her wreck never conclusively located to this day.