The Molch was a single-seat ultra-small submarine designed for operations in the coastal zone and belonged to the so-called special assault forces. During development, it was designated as "Thomas II", and production of serial models, known as "Molch", began in July 1944. The mini-submarine was equipped with a single electric motor for surface and underwater operation, which limited its combat capability. The depth of immersion was up to 60 meters, and the maximum speed in the underwater position was 5 knots. The hull consisted of three sections, with a chair for a single crew member in the center section. The Molch was built at the Deschhimag shipyard in Bremen, and 393 units were produced in total. As part of the special sabotage formation "K", these submarines were used in the Mediterranean and North Seas, making 140 trips to sea by the end of World War II.

Markings for:

• Midget submarine "Molch", training sub-unit of formation "K" (K-Verbande), 1944
• Midget submarine "Molch", formation "K" (K-Verbande), North Sea, 1945
• Midget submarine "Molch", formation "K" (K-Verbande), North Sea, 1945
• Mini-submarine "Molch", South African Museum of Military History, Johannesburg, 2000s