Good luck horse shoe mounted on submarine K10 at its launch, 1916.
© Science Museum / Science & Society Picture Library
German submarines were succesful at the start of the World War I, penetrating British coastal waters and torpedoing British cruisers. This alarmed the British Admiralty, who thought the British 'K' clas submarines were intended to spearhead the fleet, but they suffered a series of calamaties, coming to be known as the 'suicide club', and only once engaged the enemy. K10 herself did survive the war.