Try increasing Volume 1 Density to about 5 then try a color of R: 188, G: 171, B: 141 (or H:38, S:24, B: 73). A medium-ish brown. Don't go too dark I'd say. That should give you fairly natural-looking muddy water, which would seem to fit your scene I think. If it's too murky for your taste, reduce Volume1 density, but not too much. It should (IMO) be semi-opaque.
- Oshyan