All previous manned torpedoes or mini-submarines did not perform as expected since they all were constructed very fast and with the intention to used existing material. As it got obvious that these designs could not match their mission parameters, a real
mini-submarine based on technology of the U-boats was build - the Seehund .
The first of the 285 crafts was completed in September 1944 and go operational status in January 1945. It proved to be superior to all previous designs, therefore a mass production of over 1000 crafts was ordered. Used against allied supply lines in the
Schelde-Themse area, 70% of all Seehund operations had enemy contact and 90% of them survived their mission. Seehunde sunk nine merchant ships (damaging three more) and the French destroyer La Combattante .

A Seehund is now on display in the Deutsches Museum in Munich.