Even with GWX, you really only have a decent chance of downing a Swordfish. Against everything else, even if you have a flak-qualified gunner or Watch Officer, you are on the short end of a short stick, and it gets shorter fast as the war progresses.
An aircraft can fly with several holes in it. A U-boat only needs one hole in the pressure hull to make diving impossible.
Crash-dive and avoid the risks inherent in a confrontation.
