Grampus-class submarine

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.

Design
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 HMS M3 (1918). These boats were of a saddle tank type.

Service
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, HMS Rorqual (N74), survived the war.