I have been trying to get a rough mockup of our ravine scene to appear underwater. So far I have tested different lighting techniques, including colour and fog effects. I intend to look into rendering techniques that could help me next as lighting certainly helps but will definitely not be enough on its own. The bottom image is what I have achieved using various lights.
Apologies as the images are quite dark as our scene is deep underwater, so a lot of the stronger lights will likely come from the plant life.
Basic Lighting setup.
Working with light fog.
Final result with lighting.