One of the most fun (and tense) patrols I ever had was the time I decided to raid the harbor at Scapa Flow.
My sub being U-47, a Type VIIB, just like Prien's, was my inspiration to give it a try.
I approached from the western straits with decks awash but submerged to periscope depth once I was past the blockades and sub nets to avoid detection by the shore batteries. Piece of advice here is to blow your ballast (using the 'E' key) just as you're crossing over the sub net. If you do it right, that extra bit of buoyancy will float you right over the net with little, if any, damage. The sub net may still scrape your keel and make a loud racket inside your boat but it shouldn't do any damage.
It was a very successful raid.
One interesting additional note...
I later found a copy of Gunther Prien's account of his mission to raid Scapa, complete with his hand-drawn maps, and it was a great suprise to discover I had taken the exact same course as he had done when I infiltrated the harbor and then made my escape.
