I'm working on water effects right now, and I want to have transparency in my water that's dependent on how "deep" it is. In other words, it's really clear in shallow areas, and murky/opaque as it gets deeper. The way I'm thinking about doing this is adding a depth buffer to my cube map I'll be rendering to create the reflection and mainly, refraction in the water. The depth buffer should determine how far away the sea floor, and then using the depth values would determine how refractive (transparent, in this case) it is instead of just using a single alpha value, correct?

@VladR: I agree, that's not usually how water acts. Water doesn't use 6 cameras to take a constant snap shot and then wrap it around in a cube-like fashion based on its surface normals it's been consciously updating. I'm just kidding, lol

One thing I have noticed, however, is that deep water doesn't really reflect things near the top either. Look at a boat in the ocean. Whatever part is in the water, usually isn't seen. I think this could do with how the light is scattered. The ocean looks nearly opaque, but again, I haven't been near deep water in a long time.

@Hodgman: I'm using OpenGL and OpenGL ES 2.0 in some cases (where it's feasible). All the shaders I write are tested on Macs and iOS devices in an attempt to keep things somewhat compatible. I also have iOS and Mac-specific features that use define-preprocessor boundaries to deep my dev environment from compiling incorrect platform-specific stuff.

What do you mean by reflection probe? Are you talking about the viewing ray, in this case, or the position in space where I'm rendering the cubemap for reflections.

Btw, have either of you found any good books on water rendering? I've been trying to find more resources on water rendering and how to build a decent particle system, but I've only found papers.