Originally Posted by aka123

This ship thing was the case already in WWII and probably in WWI too. It was magnetic detonation under the hull. However the case is different regarding subs as much smaller damage is enough to destroy the sub and the water pressure is much higher down the deep where the subs are. Though there might be magnetic detonation to increase the chance of hit. Or maybe you are right, I don't know, but there is not that much need for it regarding subs.