There has to be a damage zon for a gun to be able to take damage, or its "platform" has to be destroyed. This would include shore installations also. Normally, an un-necessary complication to the game. The gunners will sometimes shoot until beneath the waves. Here's a video from an early FotRSU test:
... entirely too long, but at 9:40, you can see the bow gunner, in a fireball, still manning his gun station, ready to shoot his enemies, if he can only target them. Must be a good strap used to keep him there... Of note is the two torpedoes I hit the damaged Tonan Maru with at about the 8:50 mark, and the way the animated characters "die". No panic, they just "lay down" when the water gets to them. How'd they survive the explosions?...
oh well. Such is the game.
Edit: ... and I'm following KaleunMarco again... I'm not following you, seriously, I'm not...