Thanks Dune, will have a play tomorrow.
@SRB2001, yes, I'd think that could be a solution, but what's interesting about this approach, is that a node network should be able to determine distance from shore. For several reasons, like if I want to change camera angles through an animation, or want to apply these nodes to a different landscape, or whether I want to put a rock outcrop in the shore line.
What's really interesting here, is that the waves are concentric to the shore line. We just need to be able to blend this off through the function set up, which seems to be acting strangly the way this has proceeded. Ultimately, it would be good to work on things like wave overhang (curl), or have a constant that would change the wave spacing, or like Moodflow has put across, change the position compared to land for the breakers. It would be good to work this out without having to paint it manually.