I have tried lots of effects over the years and for still or slowly running water I now use only Woodland Scenics Realistic Water. It is sort of transparent, but wood grain will not show through even a quarter inch of it so you don't have to worry about it. I paint the wood darker where I want the look of deeper water and lighter and then mix in some sand color more toward shore, etc.
WS Realistic water looks very realistic for still or slowly moving water. For foam, I use white caulking. WS's product is strange stuff, a goo slightly thicker than honey. You pour it on, and thick as it is it gradually flows out level and flat - but it is a liquid: if you have the least hole in your containment it will find it and drip out. And it stays a liquid. The scene below is two years old - if I press hard on the surface i can leave a noticeable indention - it is gone by the next morning. In that scene, as recommended I "installed" the water about 1/8 inch at a time, for a total depth that varies from 1/8 inch to maybe 7/16 in places. Note in the close up of the guys fishing, there are trout in the water. Between the second and fourth (last) layer of water, I took some slivers of white styrene I cut and placed them on top of the previous layer, then poured my final layer.