Coming home from the Florida straight, I encountered two tankers, sailing south at 7kt and executed a surface attack from 1500m. Two torpedoes hit the Medium tanker, sinking her imedietely, but the only torpedo fired at Small tanker was a dud

.
I didn't have the nerve going through the whole process of outflanking and setting up another attack again, so I chased her a minute or two at flank speed, turn to perpendicular course and fired an eel from a point blank range. We were so close I almost rammed the darn thing, and was afraid the torpedo wouldn't even arm itself, but it did. Direct hit midship under the keel, and she sunk.
Now, I know that this is not the classic submarine tactic, but it was fun.
Anyone has some more crazy tactics?