easy rendering for Rhino in Windows
I normally do this by making a bitmap. The white foam is opaque and the water area is Alpha Channel transparent. Then i apply the bitmap as a decal to a surface over the water. Set the Mask to Alpha and the transparency switch in the decal properties.
In Flamingo 2, we used to use plants, with glass material or water material, and removing all texture materials from them.
Check out the fountain water in poligonal groundcover.
http://2.flamingo3d.com/whatisnew.htm (this is Flamingo 2)