the problem with airborn torpedo attack is the launch paramaters: slow, low, close; you are a sitting duck for aa and cap fighters. A submarine, if positioned correctly, can launch a nice spread without being noticed (at first). Dive bombers can fly faster, higher, and dive down with pin point accuracy. The survival rate for torpedo runs was low. As pointed out earlier, the dive bomber achieved much greater success than the torpedo bomber. Not sure the overall tonnage sunk by dive bombers vs submarines...though again, the submarine could launch ordnance in areas unreachable by planes.