Marder (Pine Marten) was a German midget submarine developed from the Neger.

[1] The craft was 8.3 metres (27 ft 3 in) long and unlike the Neger included a flooding tank in the nose allowing it to dive.

[1] Another improvement was the dome through which the pilot viewed the outside world that also served as the craft's entrance and exit was made openable from the inside.

[2] The submarine's first operations took place on the night of 2 August 1944, when Nazi Germany's Kriegsmarine's Small Battle Units made their largest effort of the war.

[1] One Royal Navy destroyer escort, HMS Quorn was sunk by a human torpedo along with one minesweeper, HMS Gairsay, and one landing craft by the German motor boats; at a cost of 41 Neger and 22 Linsen craft.