One water setting for all underwater environments can make some underwater environments look a bit off. The default settings look good for biomes such as Forests, Taigas, and Cold Oceans. Perhaps this is implemented already to some extent, but it should be made more obvious in my opinion.

But for biomes like Warm Oceans, Swamps and areas where should be either clearer or murkier the default settings is in my opinion not optimal. Swamp waters could have higher Dirt Amount values with greener tint (adjusting the Scatter and Absorption settings), while the tropical waters of Warm Oceans have lower Dirt Amount and have a warm clearer tint. Ice biomes could have colder tints, etc.

I also find underwater environments to be a bit harsh on the shading, meaning there are too much shadows in places where we would expect more ambient light. In the real world there is some extent of diffusion of light which removes much of the harsh shadows.

As an experiment I took this default environment

and set the Minimum Light Brightness to 100.0 which creates a much nicer underwater look in this area

Maxing the Minimum Light Brightness makes all places that should be dark, such as unlit caves, completely bright, so this setting is obviously not a solution, but the look itself, removing most of the harsh black underwater shadows, looks quite appropriate.

Either bump the ambient light somehow, or reduce the opacity of the direct shadows.

Thanks for a great shader though!

there is no ber-biome stuff for underwater but i have considered it, since i have some per-biome stuff for other fog effects.

i dont know how much of you suggestion will be un-addressed by the next commit, because i have changed water to be more... alive, and cleaner, and easier for gameplay

Still sounds great. It's better things are given time to be properly implemented than rushing.