Currently you're able to fire from water when surfacing it with any diving suit or when using survival fatigues. This is a great feature that goes along with diving. All you need to do is hold "X" to make sure you're above the surface.

With SDAR the problem is non-existent — you can fire regardless of your position or angle of the weapon. It works just fine.

With other, non-uw weapons, you're unable to fire when surfacing, unless your weapon is aimed at about 5 degrees up. You cannot fire despite the fact your weapons barrel and reciever group is above the water — you still have to aim your weapon high enough. This makes returning fire kinda difficult, especially if your target is not higher than you are, for example just walking at the beach.
Keep in mind you don't have to aim your weapon at angle this high when just standing on the seabed, not swimming using fins. You can fire almost parallel to the waterline.

The reason I'd like to see this angle lowered (preferably to allow firing parallel to water) is because it should be easy enough mechanically, it would contribute towards realism and most of all allow us to use non-uw weapons from the water more efficiently, for example when playing combat divers with suppressed weapons.