4. Now its time to add a bit more definition to the waves, reduce the scattering to about 150% and make your brush a bit smaller 6 is fine, set your opacity to 80%. Now you are going to paint highlights on the same layer on the edges of the waves closest to your landmasses, or if you have scalloped them well then keep them on the convex edges. Start very lightly, this white is going to look blinding at first so just go light and scatter this highlight to a few places on each wave, keeping it primarily to the center and always on the edge facing the nearest land. This step is going to take a while, but patience pays off. I know I know, I promised some definition but they still don't look like much more than chalkboard scribbles yet.
Addendum: For some added spray details you can make your brush smaller again and add a few splatters of white just in front of the leading edge of the wave.