All else equal, a near miss in water will do more damage to a ship's hull than a near miss in the air. Don't know if that's modelled in AH.
Japan designed shells for Yamato's 18" guns that would fall just below the water line for maximum effect. Turns out Yamato itself was specially vulnerable to this kind of attack due to a defect in its armored belt.
-blogs
Originally posted by humble
Bombs will react to impact in water identically to impact on land. The only difference would be penetration depth if a delayed fuse is used. Obviously a bomb will penetrate water more easily than it will earth so a .5 sec delay fuse will vary impact depth at time of explosion. Most anti ship bombs had a delay so the bomb would slice into the ships "guts" prior to exploding (same with the large 16" battleship shells) a "contact" fuse would detonate on impact with the water just like impact with ground....