The ships of the Italian Navy might have been neutralized during the Raid on Taranto and the Battle of Cape Matapan, but the Regina Maria itself was still in the fight. The Italians were years ahead in the use of underwater demolitions to attack shipping in port. Between June 1940 and August 1941, the Italians made nine attempts on British ports in the Mediterranean, but only one was successful. It was simply an issue of stamina.
The men of the secret Decima Flottiglia MAS, the 10th Assault Vehicle Flotilla, were the best combat divers in the world, but no human being had the strength and endurance to swim several miles underwater with enough equipment and explosives to cut through any obstacles and sink a ship, and then swim out again without being seen. Their only success was through the use of speedboats to sink the HMS York in Suda Bay in May 1941, which would never work again. But by July of 1941, the Italians perfected the use of the “human torpedo”: a self-propelled and nearly silent miniature submarine that divers could attach equipment to and ride or hold on to the outside of during the approach swim to the objective.
On 20 September 1941, eight divers on three human torpedoes departed from the Italian submarine Scire docked in Cadiz, Spain to attack British ships in the port of Gibralter. They avoided the extensive minefields, cut through the torpedo netting, and attached limpet mines to three ships, two tankers and a cargo freighter, which were all subsequently sunk. The frogmen swam to Spain, rejoined the Scire, and went back to Italy to be decorated.
The frogmen of Decima Flottiglia MAS would carry out monthly (mostly successful) attacks until Italy surrendered to the Allies in 1943. The raid on Gibraltar fascinated the nascent “Observer Group” and “Navy Combat Demolition Units” that were just being formed by the US Military in 1941 to tackle the problems of amphibious assault, specifically beachhead reconnaissance and destruction of beach obstacles, and their training was altered accordingly. These groups would go on to be the Underwater Demolition Teams, and eventually the Navy SEALs we know today.