1914 - 1916: Swordfish Class
An experimental submarine built in the hope of achieving a speed of 20 knots by using the steam turbine rejected from HMS Nautilus.
This submarine was developed from a design prepared for the Royal Navy by the Italian submarine designer Cesare Laurenti, whose designs were at that time in use by several navies.
HMS Swordfish was renamed HMS S1 on 1 April 1916. Captained by Commander Geoffrey Layton, she was treated as an experimental vessel and regarded as impossible to make into an effective warship, but much was learned about the operation of steam submarines, making possible the subsequent design of the steam-powered K class.
Between 27 June 1917 and 24 January 1918 was converted to a surface patrol vessel, reverting back to being named HMS Swordfish in July 1917.