Bagginsbill, you are right, but one thing that kawecki said is also true, and I don't know yet if you have taken this into account, and it may be a bit over the top for the purposes of what we want. To explain:

1. We are trying to find a "correct" system of depth cue for an underwater scene.

2. We are going to handle distance as well as the scattering of light by particles.

3. But as kawecki said, the deeper you go, the light should fade, and as he also said, and this is really finicky, the light should become bluer, until it eventually fades almost totally to black at real deep depths.

While I was looking at all the reference pictures I saw this effect but wasn't really thinking about it until kawecki mentioned it. I think for what we want to do, and the depth at which we are working (100 feet), this is maybe not really a consideration or something that needs to be taken into account.

I think in this picture you can see the darkening effect of depth.

http://fc05.deviantart.net/fs13/f/2007/047/8/f/Underwater_Light_and_Bubbles_by_Della_Stock.jpg 

But at the depths we are working at, you don't really see as much of an effect:

http://www.hawaiipictures.com/pictures/gallery/underwater/underwater11600x1200-1.jpg

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