[A Very Super Market]

I think that it's only possible to change the damage model for all ships. So we either get absolutely silly breaking apart of ships, or slow sinkings. Obviously, a small merchant hit with a torpedo would break in two, but you don't want an ocean liner doing that.

Also, the reason that bow shots sink them faster is because the ship itself is moving forwards, driving even more water at higher pressure into it's hull. Hitting the engine stops the ship completely, meaning that the watter will flood slower.