Volume Density *is* the way to do this *unless* you want to be below the surface of the water, in which case you have bigger problems since TG's water is fundamentally not volumetric (so nevermind being able to affect the density of it, it just isn't volumetric). No need for clouds, that's super hacky, again as long as you're above the water. If you want to be below the water, better off using an extremely modified atmosphere (high haze, blue color).
- Oshyan