Swing on surface of water in first person and free looking at your right back side. or look straight and you will see ocean clear with 100% visibility.
1)open editor
2)spawn a diver and a basic weapon box
3)get any weapon in there
4)go into water and you have to swim for this
5)swim on the surface while holding your weapon
6)look a little bit down into the water
7) water surface is not being rendered and uncovers underwater landscape