Hmm...I suggested above a two-stage torpedo, with the second stage being supercavitating. A variant would be a sub-launched equivalent of an ASROC: the rocket

Hmm...I suggested above a two-stage torpedo, with the second stage being supercavitating. A variant would be a sub-launched equivalent of an ASROC: the rocket pops up above the surface, flies toward the target, then drops back in the water and the supercavitating torpedo takes over. Possible advantage: ships can (perhaps!) shoot down incoming rockets or cruise missiles, but it's harder to shoot an incoming torpedo; bullets don't travel well underwater.