I actually posted an image a few months ago that had something like this; the size at which I posted here it made the effect fairly invisible (it was not as central to the scene as your splash), but it shows up pretty nicely in the poster-size render. The problem: I think it was that nice water-tree that made that render take three weeks! I think this is a great idea, and I intend to get back to it, but I'd be interested in hearing from others how it affects render times.