I would think that any ramming scenario is already factored in to the attack and defense values.
Yes, ramming was still occurring, but most of what I recall involves destroyers or other vessels ramming surfaced subs, or the collision between the cruiser Hipper and the destroyer Glowworm (which is credited as ramming by the Glowworm although it was the Hipper’s intent to ram the destroyer and the destroyer’s steering was out by then, so its turn was coincidence), or the sinking of PT-109 by the destroyer Amagiri.
The last boats that I would think of making a ramming attack in the WWII era would be capital ships, particularly undamaged capital ships. Big ships were stand off weapons (aircraft carriers and battleships.) Unless there is a long/mid range combat phase followed by a short range naval combat phase I don’t see how the attack roll would work conceptually.