Gerald Garnons Williams (pictured below) saw action in the Battle of Jutland, then trained as a sub-mariner and was appointed to his first submarine, HMS E 51 in 1917. With a crew of 31, E 51 was a heavily armed minelayer said to have carried out 25 missions laying over 500 mines during the war.

Source:
British Submarine ‘E’ Class HMS E 32, Q67706, Imperial War Museum.