Just watched an interesting show (1hr) on U-864. It left Kiel in Dec 1944 with Jet power technolgy for Japan. The sub ran into engine trouble just off Norway I believe and had to turn around. The engine problem caused it to give off more noise then it would have liked. A British sub with a brilliant young captian tracked it down. After following the German sub for nearly 2 hrs it figured out its pattern of travel. She was zig zagging at periscope depth. (Remember that couldn't really see the boat except for the occasional periscope) The British sub fired 4 minnows at her. (somewhat blindly) The first 3 missed but the last one got her. This was the only sub vs sub in WW2 and the U-864 was the one of the last German subs sunk in the war. Sorry for lack of more details.
http://uboat.net/boats/u864.htm 
The boat was also carrying a lot of mercury. You should be able to find articles on this cuz it is a big problem over there today.
