Why can’t a naval ship have chains extended on sides to keep torpedos from reach it?

Question

I’ve always thought a navy ship could have arms extending from each side, out say 20′ or so that holds some sort of draping system, like a chain or something, that extends below the bottom of the hull. Then, if a sub fired a torpedo at it, it would either explose on the chain or just get caught up in it.

In: 3375

Answer 1

Torpedoes work by detonating underneath the ship creating an air bubble. This air bubble then presses up against the keel of the ship breaking it.