Sometimes, depending on the angle this happens when looking at water. or very rarely with ice for a split second when flying up and against it.

Put the summary of the bug you're having here

What I expected to happen was...:
Normal water

What actually happened was...:
Broken water texture on top

Steps to Reproduce:
1. if you look around on the surface of water slowly you will see all water around you change color to black and/or green.

(P.S. the first pic is with opti-fine and the second is vanilla.)