The U-Boat Type II was the first class of U-Boats built in Germany after the Treaty of Versailles. They were designed using the
Finnish coastal  submarine "Vesikko " (Mink) as the prototype. This boat was designed by Ingenieurskantoor von Schepsbouw in Netherlands in 1931, which was led my German U-Boat constructors.
Being quite small boats, the so called "Einbäume" were limited by their small range and limited load of torpedoes, but were very
maneuverable and had a fast diving speed. About 46 of these coastal submarines were build, at the outbreak of the war those boats were the backbone of the German U-Boat fleet.
Since the first variants (IIA) were limited by their short endurance, later versions (IIB-IID) were lengthened to increase fuel load, the technical data shown above represent the Type IIB. While none of the German Type II boats is left today, the Vesikko is still existing as a museum ship in Finland.