Scapa Flow always is a gamble as to what's actually in there, sometimes its full othertimes empty. Dealing with the aircraft patrols just to get into the west channel can take forever. One nice little trick I found is being able to reload your torpedo's safely while in the harbor. After you sink something large, a battleship or carrier move your sub right up to it and start reloading; haven't had any DD's even notice I'm there while reloading.
Loch Ewe is great as its easy to get into, and has those 2 floating docks-almost 60k in tonnage for just 2 torpedo's
