From Mods Repository Wiki
Creating water in Radiant
1. The water textures are located in "Surface type -> water". Select which water you want and create a brush covering the entire area you want filled with water.
2. For a stream create a patch mesh and bend it to flow with your stream.
3. Some water textures will not need adjusted but depending on how you want it to look and how it is setup as a texture, you may have to fit and stretch in Surface Inspector, it will pretty much come down to trial and error.
- If you have shallow water then you only need to fill the surface, the game automatically fills underneath with what would be your player swimming underwater.
- Extreme bending of meshes or very large stretches may cause rendering issues with the water itself, just keep a close eye on it when playing.
- Some brushes that intersect the water may also cause issues when rendering the water in game.
- You can Alpha-Blend some of the water texture to get a nice transparent effect!
Creating Dynamic Water
1. Create a brush or patch as in the previous section but this time you want the texture "water_dynamic" and has a white box for the preview.
- This will look similar to other waters but now explosions will cause ripples.
- It will also change the view and lighting of the player unlike other non-dynamic water.
- DO NOT use for puddles or streams, the ripples and random small waves may break surface where you wouldn't want them and look bad.
If your water_dynamic looks very bright in the map then use the Advanced patch tool to Alpha-Blend the water patch!
Sources: Treyarch's Wiki