Yeah it definitely is a big hit for a post process, VR or no VR 
But I have a cheap method to do by having a small PP volume with blend radius follow the player camera and smoothly âfade inâ the underwater fog when the camera goes underwater (so we only need to run the gerstner lookup in blueprint, which has no cost).
Obviously it wonât look as good with that method but at least itâs cheap Also you could do it GTA 5 style (snap the camera underwater) although I have not yet seen how they handle it in first person mode.
I wonder, has any game ever done the proper way? Every game that I have seen tries to avoid by either having flat water or doing some kind of camera snap or fading.
Oh right what happened with your sub sim btw? Itâs definitely a game I would play if done right 
not many of its kind either.
There is nothing special going with the coastline (apart from the heightmap modulation, which I mentioned in previous page) itâs the same depthfade foam that the shader has (I adjusted some parameters of course).
If you feel like experimenting⌠the heightmap modulation function looks like :
http://www.mediafire.com/convkey/10b7/cll8hnov7go2lm6zg.jpg?size_id=5
You should multiply the Displacement Alpha with whatever goes to World Displacement input.
The commented variables need to be set based on your landscape (location, scale, (texture) size, and the heightmap texture), notice that there is no rotation variable (apparently I suck at rotational math) which means your landscape should have 0 rotation.
The heightmap texture can be exported from the engine as png if you have sculpted it by hand, then import it and set the texture compression to HDR to take advantage of the heightmapâs 16bit.
All of that will be optimized and have exposed blueprint parameters eventually (sometime before 2017 hopefully :D:p).