RN Submarines - May 18th

1909	C21	Submarine HMS C21 completed
1916	J5	Submarine HMS J5 completed
1916	E39	Submarine HMS E39 launched
1916	L1	Submarine HMS L1 laid down
1916	L2	Submarine HMS L2 laid down
1943	Storm	Submarine HMS Storm launched
1915	E11	E11, commanded by Lt-Cmdr Martin Nasmith passed through the Dardanelles on the night of 18 May. Surfacing off the town of Gallipoli, Nasmith captured a Turkish sailing vessel and lashed it to the conning tower to act as a disguise. This ruse failed to attract any targets, so after several days he abandoned it.
1941	HMS Tetrarch	HMS Tetrarch torpedoes and sinks the Italian merchant Giovinezza off Bengasi, Libya.
1942	HMS Turbulent	HMS Turbulent torpedoes and sinks the Italian merchant Bolsena west of Bengasi, Libya.
1945	HMS Sea Dog	HMS Seadog torpedoes and sinks a Japanese coaster north of Sumatra, Netherlands East Indies.

Source - Barrow Submarine Association