On 1 April 1963, Grampus returned to Gosport after spending three weeks under the polar icecap looking for holes in the ice.

On 11 January 1968, the French trawler Fomalhaut caught Grampus in her nets in the English Channel.

Grampus surfaced and both crews spent over three hours disentangling the nets.

In 1968 she was part of the First Submarine Squadron based at HMS Dolphin and in that year was present during 'Navy Days' in Portsmouth Dockyard.

Grampus sank on 18 September 1980 in Loch Fyne as she was being towed as a sonar target.