Foam in ocean simulator cycles?

Good evening,
the last days i tried to use the ocean modifier a bit, and i created a few good results. Than a friend sad to me, he would know, what was missing in my comp. The foam. Lots of big ocean animations just look realistic because of foam.
I guess there is a foam setting in the modifier, but i have never seen somebody using it… just in Blender internal. If i play with the values, there seems to be no changes…
Does anyone know how to use it or can link a tutorial to me? That would be very useful!