Thanks for the comments everybody! I called it a final since I'm heading down to Peru on July 1st and I won't be back in time for the end of the competition, but I'll probably (will) continue to work on it until I leave.
@TU/: the render time was
only about 30 hours, down a lot from the 120+ it took before I got rid of a pesky reflective shader on the rocks that were hanging things up. The render settings were
detail: .8
AA: 8
GI: 1/2
so I'll probably increase those a bit and play around a bit more, thanks for the suggestions
@Seth: Yep, that is a dead tree floating in the water, increasing the GI like TU suggested wll probably help make that clearer. Also, I see the lines in the water now that you've mentioned it, thanks for spotting that