SM U-1

SM U-1, also known in English as the German Type U 1 submarine, was the first U-boat class of the U-boat series of submarines produced for the German Empire's Imperial German Navy. Only one was built. The U-1 was constructed by Germaniawerft in Kiel and was commissioned on 14 December 1906. When World War I began in 1914, the U-1 was deemed obsolete and was used only for training until 19 February 1919, when it was struck by another vessel while on an exercise.

The SM U-1 was a redesigned Karp class submarine by Austrian born engineer Raimondo Lorenzo d'Equevilley Montjustin working for the German shipbuilding company Friedrich Krupp Germaniawerft. The main improvements over the export Karp class included trim tanks instead of a moveable weight, a redesigned forecastle to improve seagoing ability, a 10 cm larger diameter and strengthened pressure hull which prevented oil leakage from the external tanks, a rearrangement of the internal equipment and a heavier ballast keel.

Wikipedia