@Bryan: It may be good idea but it will definitely blow up the filter (more complex math and UI). So maybe another one. Never had success yet with shadow-highlight separation, maybe it is too subtle for me
Interesting that you applied channel mixer, I supposed that red-green and yellow-blue sliders achieve the same. Also levels... is exactly the purpose of top slider (intensity). Have you tried?
I'll try to pick some decent shots for experiments, if you want.
@StainlessS: It honestly looks in real water like the unprocessed from camera. But the picture is only fraction of how it feels. Improved balance, contrast etc makes it more impressive and IMO this is great.