Well, I'm not gonna try rendering this until tomorrow morning, as I do want a good nights rest. I've had some problems starting a large render, and can get quite disturbed and not sleep over it.
I need this for a book, yes, and, no I didn't use the volumetric desnity of the water, although I know it works kind of similar to what I did here. But I wanted a muddy shore anyway, so why not put some mud colour over the whole botom at the same time.
I figured that this render at 4800 px wide would take about 6 times it did for a 1600 px render, which was 2.45 hours. So I might try a higher detail. On the other hand, I did some tests a while ago and didn't see a huge improvement. It might be easier to (like TG) do a slightly larger render and decrease size in PS.
---Dune