@ Richard: indeed, part of the whole sea that's pushed up and aside, by using a simple shape, twist/shear and a distribution shader (and such).
@ KevinF: I'll keep that one in mind.
@ jbest: 5 hours or so @ 0.5 and 5AA The fall is indeed too glassy. Actually it's too big to be glassy, but you sometimes have these thin and fine waterfalls, which are very transparent. I might use this technique for such a fall.