I followed the advice today which someone posted here, can't recall his name though. He said there is a great hunting-ground at the Strait of Florida (the wide channel just below Florida).
Thought I'd take a look, see if it's worth it...
....and WOW!
This place is tanker-heaven! All the large tankers pass through here, either unescorted or escorted by a larger tanker

I just passed some bad weather, which further increases the fun. Now it's just one hit on the stern and let the waves do the rest
So far I've bagged 106k tons, with 10 more torps to spend. I can advice every depressed person to spend a few weeks here. You'll feel better instantly after seeing the rediculous amount of tankers passing through here!
I've been here for 3 weeks now, and so far encountered just 1 Catalina (which missed) and 1 torpedo boat.
Most tankers I saw had few defensive armamant, so come 'on over!
EDIT: It was Predavolk who suggested it. Here's the link:
http://www.subsim.com/radioroom/show...highlight=Balz