There have been incidents I know of with U-Boats saving crews early in the war, I forget the specific examples, but one U-Boat stayed with the passengers of a ship it sank, radioing their position to Allied forces. Unfortunately the allies reponded by sending a plane to attack the U-Boat, and it was forced to escape. The passengers were later rescued, though.
Another funny incident I have heard of (again, I forget the specifics), but it happened very early in the war when two Allied Suka dive bombers tried to attack a surfaced U-Boat... their bombs skipped off the surface of the water, came up short, and exploded in the air, downing both planes. The U-Boat crew then rescued the pilots.
