I was watching Megasubs on Disocvery Channel last few week when they featured the Swedish Gotland class subs ans the U212 from the German navy
Apparently they showed the engine in operation, and showed the Gotland running under AIP system..quite quiet but not really
Next was the U212, using fuel cells they actually showed us the engine running in diesel(noisy) and after a push of a button, into slient mode literally SLIENT.
Maybe the U212 was a much better choice than the second hand Vastergotland class due to higher end technology and capabilities? and porbably looks nicer too?