This is not happening for everyone. My buddy on the same server right now does not have this issue, it's perfectly clear, yet mine looks all washed out 100% of the time; just like your screenshot. He can even see under water from the surface. With that said, I've had this issue long before the last update. Our settings are also matching, same 980ti.

Are you running the game with -sm4 launch option? I do that to increase my frame rate, and I get a lot of "fog" in our caves. Tends to clear up when I go outside, or if I take that option off.