These videos, from the Naval Archives in Washington, DC., are made available through the kind cooperation of Bolling Smith, of the Coast Defense Study Group, to whom I say thank you very much. 

"Sneak Craft" is the collective term for very fast or deceptive methods of delivering explosives above or below the surface to destroy allied shipping and waterway locks.  In the video you will see how each type of Sneak Craft was used.  Of note is the use of underwater breathing apparatus and the fact that, in the Mediterranean alone, Sneak Craft were responsible for sinking or damaging 150,000 tons of Allied shipping. 

There were basically four categories of Sneak Craft:

Swimmer: Men would swim out to the target (up to 2 miles), place an explosive charge, set a four hour timer and swim away.  Note the use of underwater breathing apparatus.  Swimmers also blew up locks along the inland waterways.

Human Torpedo:   Despite what you might think, this did not involve suicide.  It was a modification of a torpedo to carry two men and two detachable 280 pound warheads.  The four speed vessel could maneuver left and right, up and down and had electric ballast pumps.  Only the pilot's eyes were visible when they cruised on the surface, making detection extremely difficult and they were practically impossible to detect at night.  Upon arrival at the destination the explosives were attached under the keel of the target.  Then they set the timers and escaped.  In the Spring of 1944 the German's had their own human torpedo design.

Midget Submarine:  Developed by the Germans, with a range of a mere 75 miles, it was not very successful due to heavy batteries, 4 knot speed and difficulty in any but the calmest seas.  After two 15 boat sorties, during which all boats were lost, the design was abandoned.  The video details additional successor designs of this technology that ultimately could cruise up to 500 miles and stay at sea for a week.

Torpedo Boat:  With a top speed of 35 knots, the Italian designed craft with two Alpha Romeo engines, would deploy their torpedo, then turn sharply to make their escape.  This theory didn't work out in practice as the ship's gun crews were able to shoot these vessels out of the water or drive off the attacks before damage was done.  The German design, carried two stern mounted torpedoes, arranged so that one was fired on the run in and one on the retreat.  Ultimate performance, like the other designs, was not impressive.

Explosive Boat:  An Italian design, with speeds up to 33 knots, this design had a propeller that could rotate up allowing the boat to traverse torpedo nets with surprising ease.  Easy to spot and extreme vulnerability to gunfire, they were categorized more as a nuisance craft than effective offensive ones.  The Germans had their own design, with an 800 pound charge.  The pilot would aim the boat at his target, lock the controls and at the last possible second, jump overboard.  Near the end of the war the Germans developed a radio controlled boat and attacked with one pilot boat and two explosive boats.  The guns of the escort ships blasted these craft out of the water with almost 100 percent success.

 Click Here to access extensive background information on the Mark 13 and Mark 15 torpedoes.