There's a layer of murkiness on the water that flickers in chunks. It seems slightly view dependent. The camera usually moves a bit when you're standing still and the chunk pattern changes in time to the slight camera bob. Also as I look around it completely changes it.

I have the most ultra settings all enabled and am playing on an ultra wide display with the 4K texture pack. I thought it was some dlss issue but I disabled that and it still happens.