Grampus Class: Minelaying Submarines
Originally intended to be Porpoise class, five boats were to be the same specification as Porpoise but they were changed and built with internal fuel tanks.
There still appears much confusion as to the name of this class of submarine. They were known as Porpoise, Narwhal or Grampus class depending on the source of information. Since Grampus was one of the Chatham boats, this site will call them GRAMPUS class.
They were 5' greater in length, 4'6" less beam but with an increased displacement to the original Porpoise.
Two of the five, Grampus and Seal were built at Chatham. Grampus had a short career of just 39 months. She was lost off the coast of Sicily in 1940. Seal survived the war giving service to both the Royal Navy and after being captured in 1940 served in the German Navy.
Rorqual was the only other survivor of the war and she was scrapped in 1946.
As a class, they accounted for laying in excess of 2,000 mines, the sinking of two submarines, three torpedo boats and thirty plus surface ships.