Earlier I tried a canyon scene with a rushing river below. Render took 20 hours and I was not overly impressed with it. So as a test I attached a water shader to a dark surface layer as a child. I fully expected it to not work, but it did. Now it needed a nearly flat surface, which fortunately was already there. And the surface layer had to have like a 5 degree max slope constraint with a very low fuzzy zone. Render time was reasonable, less than 3 hours. I doubt it'd work for scenes close to the water's edge. I'll check that out later.