OK, this is REALLY kludgy - a 30 second paint job, but it shows how you might use the foam brush.

If I was doing this for real, I'd probably reduce the size of the foam brush, include the semi-transparent water material foam brush object, along with this one that is pure white, and basically do a much more careful job of painting. I'd use the combination of the pure white foam object and the semi-transparent foam object so that the bow of the boat would show through a little more. Plus, it would look more natural to have a mixture of crashing foam and water on the bow. Reducing the size of the foam would certainly look more natural. And then I'd shift my viewpoint of view around in the Viewports, so that I could do a more careful job of painting the bow and that wave top the boat is crashing into. Plus do a much more careful and deliberate job of painting the buoy with the foam bits.

But, you get the idea, I hope (despite my poor, rushed effort here). The painted wake and splashing along the waterline certainly adds a sense of motion to the scene.