This video tutorial goes through the steps to create an underwater environment in VRay for Rhino 8. The key steps in this video can be found below:
00:00 - Introduction
00:51 - Adding a sky environment
02:00 - VRay 'Infinite Plane' to create the water
03:47 - Creating a rocky material for the seabed
06:02 - Adding a displacement to the rocky material
08:00 - Adding a 'Noise' map to create the water texture
09:58 - Adding a 'Volumetric Environment' to create the underwater effect
13:44 - Lighting effect using a 'Spot Light'
16:35 - Adding lens effects and vignettes
The textures used in this video can be found via this link:
https://polyhaven.com/a/aerial_rocks_04