So, BoxMask looks ugly, if you think about it and is not suited what I want to achieve. For smaller waters this suits.
What I want to achieve is something like in Source Engine(taken from Gary’s Mod):
As You can see, When in Water, youo see the fog. Everything that’s above water is not affected by the Fog. But in the distance you can see that the Fog is still applied.
Scene Depth doesn’t seem to be suited for what I want at all.