CPU is some years old, but still rated good, graphics card's release was two years ago and was bought this summer, the RAM is kind of a bottleneck in my system, but I don't see how it could be responsible for this visual bug.
GPU doesn't really mean a lot in this title. I mean, I can get 60FPS with a old Intel Core 2 Quad that's overclocked and a GTX770. (yeah, i pushed that to the very edge of it's life. Still use it as a backup server too.)
The RAM you've got isn't terrible either. Which is why i think it's either some setting, or the client not recognizing something. Needs logs to be able to tell more though.
It's that way right from the start, though it gets worse the longer I play (and the more Zombies die in those waters).
Initially, when I had first build my base in the lake everything was in order, but it got gradually worse.
It also isn't untransparent from every angle, when looking at certain angles I can see through the shroud or at least partially, also when I use a scope I can see farther.