On the topic of the XXI here is something designed of that design:
http://www.projectboats.com/whiskeysub.html
"The initial design was developed in the early 1940s as a sea-going follow on to the S-class submarine. As a result of war experience and the capture of German technology at the end of the war, the Soviets issued a new design requirement in 1946. The revised design was influenced by the German Type XXI submarine and was developed by the Lazurit Design Bureau based in Gorkiy."
And for any of you rich people if you got a half a mil. laying around you may feel like owning this lol