Water in Call of Duty: Black Ops 3 is composed of 3 different parts. Depending on how you'll be using your water, you might not need all 3 parts.
- Water Texture
- Clip Water
- PBG Box
Primarily, and most importantly all water needs an actual texture. These textures can easily be found by going to usage in the Texture Browser(T) and selecting Water.
While a water texture will do the visual aspect of rendering water for you, clip_water will allow it to act like proper water. Allow players to swim in it, or walk slower depending on how submerged they are & proper effects upon impact. Create a brush & apply the water_clip texture to it, and have it cover your desired area.
Finally, a PBG Box, found in the Entity Browser(B) will allow you to discolour the view of players inside the selected area. Much like a reflection probe, place the PBG Box and resize it to your liking. Then it's time to edit it's KVP's. As a start, you'll want to:
- Enable USE_UNDERWATER
- Edit the KVP's underwater_absorbtion & underwater_mix.
Of course, you can mess around with more KVP's to see what fits your liking the most.