Water is dark or brown

Whenever I am under water, the water is either black or just too damn dark. Above water, instead of water, there’s just a big, gray patch.

^this^ video has some screenshots of my problem. NOT A RICKROLL/TROLL (I promise :3)

  1. Open steam library
  2. Right click “Garry’s mod” and click “Properties”
  3. Now click “set launch options”
  4. put this code “-dxlevel 81”
  5. Should fix this type of issue.