Nice concept.
And as shown in the reply by "Mazak", the "foam attractor object" can be any object, not just a terrain, as many believe, I think.
I use the same method as "Mazak", e.g creating the wake around/behind a boat: you turn the boat 180 degr. make it larger, and flatter and invisble, positioning it so it gives the desired effect.
I'll post another screendump next.
