Ahh,there you go then,a mod,that explains it.
I didnt know they were actually constructed as early as 1940 (if you are really,really,really good I mean),didnt know the tech was available then for a true submarine.I have yet to experience the XXI,didnt even see it in stock game,but I dont care,now I have GWX3GOLD I am perfectly happy to start all over in one of the cosy little Type IIs

(quite like em,albeit awful speed and armament)
Thanks.