Whilst I was off the coast of Scotland last year on a Royal Navy Nuclear Submarine we surfaced for a few hours and I went up the conning tower to get some fresh air and the weather was quite bad, a force 8 I think, and the boat was rolling around quite badly even later on when we dived to 60 meters, and thats on a 5000 ton nuclear submarine, imagine what it was like on a U-Boot 60 years ago.
BTW: Ive been to Scapa Flow on a boat too a couple of years ago and was quite impressed that the German U-Boats got anywhere near the place looking at the terrain and the weather, these men have my respect from one submariner to another, they had it hard, very hard and what they achieved paved a huge cornerstone in todays modern submarine warfare.
Respect your enemys past and present 