This 2,5 tons vessel also had a plexiglass cockpit like the Marder. First and foremost it was build for high underwater speed attack runs. In trials she reached a maximum speed of 17 knots while submerged.
3 prototypes were built. The first was heavily damaged on 18 Jan, 1945 after a collision with a boat, the other two were blown up on 1 May 1945 in Pötenitz (Trave).