Friends and family of some of the 75 crew who died when HMS Affray sank in April 1951 have marked the 60th Anniversary of the disaster.
The Royal Navy A-class submarine sank while on a training exercise, the cause of which is still disputed today.
At the time, the disaster, the worst British submarine accident since World War II, attracted worldwide attention.
All 75 on board, which included 50 crew, 21 officers on training and 4 marines, perished.
Herbert Allen, the last living member of the vessel's crew, was transferred to another submarine the day before HMS Affray set sail.
He said the aim of putting two wreaths and 75 rose petals into the sea above the wreck was to keep the memory alive of those who had lost their lives.
During the short service the poem Lest We Forget, which was written by a sailor on watch during the initial search for the submarine, was read by Mr Allen's son Martin.
Herbert Allen said he was "very moved, very touched, appreciative of being able to do something on this occasion".
HMS Affray left Portsmouth on 16 April 1951 and submerged about 30 miles south of the Isle of Wight at 2115 BST, but failed to resurface when it was due at 0830 BST off Start Point.
A search and rescue operation was launched, with 26 ships and submarines and every available aircraft involved.
It was eventually found 7.5 miles north west of Alderney two months later.
The Royal Navy's official inquiry concluded HMS Affray sank because the snort mast, the tube through which the diesel engine "breathed" while the submarine was at periscope depth, snapped because of metal fatigue.
However, Herbert Allen said he thought differently. He said: "My own personal explanation is that it was a battery explosion that would have originated the incident in the first place."
Martin Allen said there were plans to start raising funds to have two plaques, engraved with the names of the crew, placed in Portsmouth and Alderney.