The dive was part of a commemorative event in which the Dorset branch of the Submariners Association held a service for survivors and relatives of the dead.

Shon Roberts, Janine Jewry, Mac Jessop and Steve and Annette Sansom dived the wreck from Breakwater Dive Centre's charter boat Goose. HMS Sidon lies upright and intact in 35m of water, covered in marine life and snagged fishing nets.

The divers touched down on the sub's conning tower and, poignantly, eyed the closed main hatch through which rescuers desperately fought to save crew as the sub sank in Portland Harbour in June 1955.

HMS Sidon was moored to a supply ship when a torpedo exploded due to a fuel leak. There was no warhead, but the exploding hydrogen peroxide propellant still killed crew and caused the submarine to fill and sink.

HMS Sidon was refloated and towed in to Chesil Beach, where the dead were removed and buried at Portland Cemetery. The sub was later taken out to sea and sunk as a practice target.

Guests at the event included Mrs Gill Dash, whose father Surgeon Lt C Rhodes was posthumously awarded the bronze Albert Medal. The supply vessel medical officer repeatedly entered the sub to rescue several crew, before succumbing to smoke and fumes.

Mrs Dash wore her father's medal at the unveiling of a memorial stone on Portland Heights. Her husband, Fred, accompanied the divers out to the wreck and watched proceedings from the deck of Goose.