HMS P311

HMS P311 was a British U-class submarine built by Vickers-Armstrongs in Barrow-in-Furness. Launched in March 1942, she was commissioned into the Royal Navy in July 1942. She is notable for being one of only two submarines during World War II to be lost in action without a single survivor, and for the mysterious circumstances surrounding her disappearance.

P311 was assigned to the Mediterranean theatre. Her primary mission was to participate in Operation Husky, the Allied invasion of Sicily. Specifically, P311 was tasked with landing a team of Special Boat Service (SBS) commandos near the coast of Sicily, whose mission was to sabotage Italian coastal defenses prior to the main landings. This team was equipped with folbots (collapsible canoes).

The submarine departed from Malta on December 28, 1942, and was never heard from again. It was presumed that she had struck a mine. All 71 crew members and SBS operatives on board were lost.

For over 70 years, the location of HMS P311 remained a mystery. In May 2016, the wreck was discovered by an Italian diver near the island of Tavolara, off the coast of Sardinia. The submarine was found largely intact, sitting upright on the seabed at a depth of approximately 90 meters. The condition of the wreck suggests that the submarine may have sunk rapidly after encountering a mine or suffering some other catastrophic event. Notably, the torpedo hatches were still sealed, indicating that the boat was lost before it could engage in any offensive action. The Italian government has designated the wreck site as a war grave.