In refurbishing the Wagon Road Creek tunnel area I wanted to upgrade the creek. It was originally made with Woodland Scenics Realistic Water and clear caulk for the rapids. The froth was added with white paint.
This lacked three dimensions but looked reasonably good.
While I was playing around with tile grout I realized it could be utilized for foamy, frothy water. A quick experiment showed that mixing it with gloss medium produced a realistic froth.
I am using a Sauterne Spectra Lock Mini-Unit Part C Color Powder tile grout , I don't know what other ones will do. This one works.
The tile grout is mixed in with the gloss medium. Don't worry about the white gloss color it will disappear when the medium dries.
The mixture is either dabbed on to make large areas or the brush is dragged. In dragging the brush should be dragged against the flow of the "water". Not like that picture shows.
The foam is generally on the front side of the waves and rocks.
(Click the images below to enlarge)
I am pleased with this technique, now the water looks as good in person as it does in the pictures.