Now, I need to make some underwater renders.

Just as an aside, I recently felt the need for a fluid sim in one of my renders. Of course, Carrara doesn't do that. I decided to have a go in Blender. The fluid sim in Blender (after a tutorial or two) turned out to be incredibly simple. I created the sim in Blender and exported it to Carrara for mats and rendering. Turned out pretty good. Now I can add Ron's waterline brushes to the mix. I need to do another fluid sim. :)