The Grampus-class submarines were a group of minelaying submarines built for the Royal Navy in the late 1930s. These boats are sometimes referred to as the Porpoise class from the single prototype, HMS Porpoise built in 1932. Five boats to a modified design were built between 1936 and 1938. The ships were all named after marine mammals.
The naval mines were stored in a special "gallery" with a conveyor belt built into the outer casing as pioneered by the converted M-class submarine . These boats were of a saddle tank type.
Boats of this class were used extensively in the Mediterranean, particularly as part of the supply effort to the besieged island of Malta in a service nicknamed the "magic carpet".
Only one,, survived the war.
| Ship | Builder | Launched | Fate | |
|---|---|---|---|---|
| Vickers, Barrow | 30 August 1932 | Sunk by Japanese aircraft in the Malacca straits, 16 January 1945. | ||
| Chatham Dockyard | 25 February 1936 | Sunk by Italian torpedo boats and off Sicily 16 June 1940. | ||
| Vickers, Barrow | 29 August 1935 | Sunk 30 July 1940 by German aircraft near Norway. | ||
| Vickers, Barrow | 21 July 1936 | Arrived Newport to be broken up 17 March 1946. | ||
| 2 December 1937 | Sunk by Italian torpedo boat Generale Achille Papa off Cyrenaica 30 July 1941. | |||
| Chatham Dockyard | 27 September 1938 | Captured by the Germans in the Kattegat 4 May 1940 after sustaining mine damage, commissioned as the UB, scuttled 3 May 1945, but later raised and scrapped. |