During World War II, a special K-Verbände (K-Verbände, full name Kleinkampfverbände der Kriegsmarine) was created in the German Navy. Its tasks were to carry out sabotage and assault operations on rivers, in the sea and in the coastal zone. The unit included units of sabotage boats, manned torpedoes, combat swimmers and various types of mini-submarines. One such submarine was the single-seater 'Molch', designed for operations in the littoral zone. They were equipped with a single electric motor for surface and underwater travel, the depth of immersion was up to 60 meters, the maximum speed in the underwater position was 5 knots. The construction of the 'Molch' was carried out at the Deschhimag shipyard in Bremen, in total 393 units were delivered to the Kriegsmarine. These submarines were used in the Mediterranean and North seas as part of the "K" compound. Another type was the 'Seehund' which had a larger size, improved seaworthiness and a crew of two. Also, they already had two separate engines for surface and underwater swimming. By the end of the war, 285 units had been built, and they are considered the best type of German ultra-small submarines. After the end of the war, several 'Seehund' served in the French Navy.
