The Grampus-class submarines were a group of minelaying submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s built for the Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

  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 mines were stored in a special "gallery" with a conveyor belt built into the outer casing as pioneered by the converted HMS M3

HMS M3

HMS M3, built by Armstrong Whitworth, Newcastle Upon Tyne was an M class submarine of the Royal Navy.M3 was ordered from Armstrong Whitworth on 28 July 1916 and laid down at Elswick in December as an M-class submarine, but was referred to as K20. She was launched on 19 October 1919, and...

. These boats were of a saddle tank

Saddle tank (submarine)

Saddle tanks are a type of ballast tank configuration fitted to mid-era submarines, those of World War II.Saddle tanks are fitted in pairs external to the pressure hull, one on each side, in a similar manner to that of a horse's saddle-bags, the positioning of which they resemble in appearance.-...

 type.

Service

They were used extensively in the Mediterranean, particularly to supply the besieged island of Malta

Siege of Malta

Siege of Malta may refer to:* The Siege of Malta , in which the Ottoman Empire failed to dislodge the Knights Hospitaller** Siege of Malta, 1570 work of the Cretan writer Antonios Achelis, about the above...

 in a service nicknamed the "magic carpet"

Malta Convoys

The Malta Convoys were a series of Allied supply convoys that sustained the besieged island of Malta during the Mediterranean Theatre of the Second World War...

.

Only one, HMS Rorqual, survived the war.

Boats in class

Ship	Builder	Launched	Fate
Porpoise (N14) HMS Porpoise (N14) HMS Porpoise was one of the six ship class of Grampus-class mine-laying submarine of the Royal Navy. She was built at Vickers Armstrong, Barrow and launched August 30, 1932. She served in World War II in most of the naval theatres of the war, in home waters, the Mediterranean and the far east...	Vickers Vickers Vickers was a famous name in British engineering that existed through many companies from 1828 until 1999.-Early history:Vickers was formed in Sheffield as a steel foundry by the miller Edward Vickers and his father-in-law George Naylor in 1828. Naylor was a partner in the foundry Naylor &... , Barrow	30 August 1932	Sunk by Japanese aircraft in the Malacca straits, 16 January 1945.
Grampus (N56) HMS Grampus (N56) HMS Grampus was the lead ship of her class of mine-laying submarine of the Royal Navy. She was built at Chatham Dockyard and launched on 25 February 1936. She served in the Second World War off China before moving to the Mediterranean Sea. She was sunk with all hands by the Regia Marina on 16 June...	Chatham Dockyard Chatham Dockyard Chatham Dockyard, located on the River Medway and of which two-thirds is in Gillingham and one third in Chatham, Kent, England, came into existence at the time when, following the Reformation, relations with the Catholic countries of Europe had worsened, leading to a requirement for additional...	25 February 1936	Sunk by Italian torpedo boats Circe and Clio Spica class torpedo boat The Spica-class were a class of torpedo boats of the Regia Marina during World War II. These ships were built as a result of a clause in the Washington Naval Treaty, which stated that ships with a tonnage of less than 600 tons could be built in unlimited numbers...  off Sicily 16 June 1940.
Narwhal (N45) HMS Narwhal (N45) HMS Narwhal was one of the six ship class of Grampus-class mine-laying submarine of the Royal Navy. She was built by Vickers Armstrong, Barrow and launched 29 August 1935. She served in the Second World War in home waters...	Vickers Vickers Vickers was a famous name in British engineering that existed through many companies from 1828 until 1999.-Early history:Vickers was formed in Sheffield as a steel foundry by the miller Edward Vickers and his father-in-law George Naylor in 1828. Naylor was a partner in the foundry Naylor &... , Barrow	29 August 1935	Sunk 30 July 1940 by German aircraft near Norway.
Rorqual (N74) HMS Rorqual (N74) HMS Rorqual was a British mine-laying submarine, one of the six ship class of Grampus-class of the Royal Navy. She was built by Vickers Armstrong, Barrow and launched 27 July 1936. She served in the Second World War in the Mediterranean and in the far east...	Vickers Vickers Vickers was a famous name in British engineering that existed through many companies from 1828 until 1999.-Early history:Vickers was formed in Sheffield as a steel foundry by the miller Edward Vickers and his father-in-law George Naylor in 1828. Naylor was a partner in the foundry Naylor &... , Barrow	21 July 1936	Arrived Newport to be broken up 17 March 1946.
Cachalot (N83) HMS Cachalot (N83) HMS Cachalot was one of the six ship class of Grampus-class mine-laying submarine of the Royal Navy. She was built at Scotts, Greenock and launched 2 December 1937. She served in World War II in home waters and the Mediterranean...	Scotts Scotts Shipbuilding and Engineering Company Scotts Shipbuilding and Engineering Company Limited, often referred to simply as Scotts, was a Scottish shipbuilding company based in Greenock on the River Clyde.- History :...	2 December 1937	Sunk by Italian torpedo boat Papa Spica class torpedo boat The Spica-class were a class of torpedo boats of the Regia Marina during World War II. These ships were built as a result of a clause in the Washington Naval Treaty, which stated that ships with a tonnage of less than 600 tons could be built in unlimited numbers...  off Cyrenaica 30 July 1941.
Seal (N37) HMS Seal (N37) HMS Seal was one of six ships of the Grampus-class mine-laying submarines of the Royal Navy. She served in the Second World War and was captured by the Kriegsmarine and taken into German service as U-B...	Chatham Dockyard Chatham Dockyard Chatham Dockyard, located on the River Medway and of which two-thirds is in Gillingham and one third in Chatham, Kent, England, came into existence at the time when, following the Reformation, relations with the Catholic countries of Europe had worsened, leading to a requirement for additional...	27 September 1938	Captured by the Germans in the Kattegat Kattegat The Kattegat , or Kattegatt is a sea area bounded by the Jutland peninsula and the Straits islands of Denmark on the west and south, and the provinces of Västergötland, Scania, Halland and Bohuslän in Sweden on the east. The Baltic Sea drains into the Kattegat through the Øresund and the Danish... 4 May 1940 after sustaining mine damage, commissioned as the UB, scuttled 3 May 1945, but later raised and scrapped.