German Type II submarine The Type II U - boat was designed by Germany as a coastal U - boat , modeled after the CV - 707 submarine , which was designed by the Dutch dummy company NV Ingenieurskantoor voor Scheepsbouw den Haag ( I . v . S ) ( set up by Germany after World War I in order to maintain and develop German submarine technology and to circumvent the limitations set by the Treaty of Versailles ) and built in 1933 by the Finnish Crichton - Vulcan shipyard in Turku , Finland . It was too small to undertake sustained operations far away from the home support facilities . Its primary role was found to be in the training schools , preparing new German naval officers for command . It appeared in four sub - types . Background . Germany was stripped of her U - boats by the Treaty of Versailles at the end of World War I , but in the late 1920s and early 1930s began to rebuild her armed forces . The pace of rearmament accelerated under Adolf Hitler , and the first Type II U - boat was laid down on 11 February 1935 . Knowing that the world would see this step towards rearmament , Hitler reached an agreement with Britain to build a navy up to 35 % of the size of the Royal Navy in surface vessels , but equal to the British in number of submarines . This agreement was signed on 18 June 1935 , and was commissioned 11 days later . Design . The defining characteristic of the Type II was its tiny size . Known as the " Einbaum " ( " dugout canoe " ) , it had the advantages over larger boats of the ability to work in shallow water , diving more quickly , and being more difficult to spot due to the low conning tower . However , it had a shallower maximum depth , short range , and cramped living conditions , and could carry few torpedo es . The boat had a single hull , with no watertight compartments . There were three torpedo tubes forward ( none aft ) , with space for another two torpedoes inside the pressure hull for reloads . A single 20 mm anti - aircraft gun was provided , but no deck gun was mounted . Space inside was limited . The two spare torpedoes extended from just behind the torpedo tubes to just in front of the control room , and most of the 24 - man crew lived in this forward area around the torpedoes , sharing 12 bunks . Four bunks were also provided aft of the engines for the engine room crew . Cooking and sanitary facilities were basic , and in this environment long patrols were very arduous . Most Type IIs only saw operational service during the early years of the war , thereafter remaining in training bases . Six were stripped down to just a hull , transported by river and truck to Linz ( on the Danube ) , and reassembled for use in the Black Sea against the Soviet Union . In contrast to other German submarine types , few Type IIs were lost . This , of course , reflects their use as training boats , although accidents accounted for several vessels . These boats were a first step towards re - armament , intended to provide Germany with experience in submarine construction and operation and lay the foundation for larger boats to build upon . Only one of these submarines survives to this day ; the prototype CV - 707 , renamed " Vesikko " by the Finnish Navy which later bought it . On February 3 , 2008 , The Telegraph reported that U - 20 had been discovered by Selçuk Kolay , a Turkish marine engineer in of water off the coast of the Turkish city of Zonguldak . The paper also reported that Kolay knows where U - 23 and U - 19 are , scuttled in deeper water near U - 20 . Type IIA . Deutsche Werke AG , of Kiel built six Type IIAs in 1934 and 1935 . Type IIB . Deutsche Werke AG , of Kiel , built four Type IIBs in 1935 and 1936 , Germaniawerft AG , of Kiel , built fourteen in 1935 and 1936 , and Flender Werke AG , of Lübeck , built two between 1938 and 1940 , for a total of twenty built . List of Type IIB submarines . There were 20 Type IIB submarines commissioned . Type IIC . Deutsche Werke AG , of Kiel built eight Type IICs between 1937 and 1940 . List of Type IIC submarines . There were eight Type IIC submarines commissioned Type IID . Deutsche Werke AG , of Kiel built sixteen Type IIDs in 1939 and 1940 . List of Type IID submarines . There were 16 Type IID submarines commissioned Ships in class . See list of German Type II submarines for individual ship details