Although Italy had a good size navy in the beginning of the war, it lacked two vital elements that would make its naval forces effective. Those elements were aircraft carriers and radar. Unfortunately for Italy, the Allies had both. The Siluro a Lenta Corsa (Slow Approach Cylinder), also known as the Human Torpedo, or affectionately called Il “Maiale” (The Pig), was an Italian invention to attempt to even the odds. The Maiale was made to attack British warships while in port. The Human Torpedo was not really a torpedo, but an actual underwater tubular shaped craft that held two people (Driver and Pilot). The entire fore section of this craft was made of high explosives that was able to clamp to the bottom of the keel of an unsuspecting ship.
The explosive had a time delayed fuse which gave the pilot and driver time to get away once the warhead was clamped. The craft itself was very silent due to the electric motor used for propulsion. The Maiale had a top speed of 4.5 knots and a range of 24 kilometers at 2.3 knots. The crew wore rubberized suits as well as oxygen containers for long periods of time underwater.
The greatest success achieved by the Maiale was on December 19, 1941 when Lieutenants Luigi Durand de la Penne and Bianchi successfully navigated the Maiale’s into the harbor defenses of the port of Alexandria, Egypt and severely damaged two British Battleships (H.M.S Valiant and the H.M.S. Queen Elizabeth). If it was not for the shallow bottom, these ships would have been lost.
Source: The Mediterranean. World War II. Time Life Books, A.B.C.Whipple; Alexandria, Virginia.