Guess they don't have proximity fuses then tho...

Submarines with the 3"/50 anti-aircraft guns were not issued with air burst shells or the fuse setters needed for them (proximity fuses didn't come until later). As noted above, the other guns were not capable of the anti-aircraft role, save possibly the 5"/25, but that was never issued anti-aircraft ammo either.

The reason why you can hit aircraft fairly easily with the deck guns in SHIV is that the aircraft behavior has little to do with reality.

edit: rather important word left out. ;)

Try shooting down a plane and having it spiral out of control INTO your sub's conning tower

After the smoke cleared, well....

Chalk one up for the Japs :)