BaronVonSchnitzel,
I was as Scapa Flow just a few patrols ago, and remember the fence too...
I uploaded a small map for future trips there.
Below is a picture of a safe-opening at Scapa. It's for entering the harbor from south to north, at the most narrow point of the entrance.
Press F5 in the game, and zoom-in your map view to 2500m (map zoom-scale is displayed in the lower-left hand side of the map). The 'east-west' measuring line I drew is close to where the fence is.
There's an opening about 1600-meters from the right-hand side of the shore. Just enter there and it should be fine.
