CV 707 1933-36
Contrary to others, the origin of the fifth Finnish submarine was based on the needs of the Germans. Besides large ocean type submarines, the Reichsmarine needed a smaller, entirely new coastal boat type which could also be used for training.
The Germans contacted Finnish Crichton-Vulcan and asked the dockyard to build a prototype of the new type. After getting permission from the Finnish government, the dockyard made the contract on constructing the submarine now called CV 707 in 1931.
During summers 1933 and 1934, the German Navy made trails and exercises with the boat on Finnish waters. CV 707 had a German commander, but operations took place under the supervision of a Finnish submarine officer.
Germans accepted the CV 707 as the prototype of the future Type II. During 1935-36 the Deutsche Werke in Kiel constructed six nearly identical boats named Typ IIA (U 1-6) for the German Navy, now called Kriegsmarine.
The contract between IvS and Crichton-Vulcan made it possible to buy a CV 707 for the Finnish Navy. Unfortunately the funds of the navy were bare and it was not until summer 1935 when the first all Finnish crew could sail with this top modern submarine. The vessel was added to the submarine flotilla and on 1 April 1936 it was christened as Vesikko (meaning European mink, Mustela lutreola).