I regularly check the "What happened on..." section over at uboat.net and click through the ships sunk or damaged especially in '44 or '45.
When I look at some of the locations where those ships have been torpedoed I always wonder "How on earth did the sub manage to do this?", sink ships in the Channel or in St. George's strait or close to the English coastline with all the planes, DDs, mines and whatever around.
So my nomination would be just about every ship sunk in late '44 or '45.