i know there was a free displaced "froth" /"foam" material here some years ago, but how that stands up to current render demands I dont know, there are programs that have fluid simulations capabilites, blender is one, maybe ask one of the Wave modellers like Nerd3d, his waves on the beach series has a setting for a large wave and quite an extensive read me on setting up the render if i remember correctly. It also depends on how many material zones your model has, maybe a number of layers in postwork could achieve the effect.

The only other suggestion I have if the model is to be used in a still image is some postwork with a blur type brush in your image software to create that blended softness of the white water.