Having a hard time posting a pic so here is a description:
Typical spar bouy; a cylinder with ballast at the bottom and floatation at the top so it stands upright in the water.
Along the shaft are are discs with one flat side and one convex side. Those with the convex side up are fixed to the cylinder, those with the convex side up are “free” so that the disc can slide up and down the cylinder.
When water pushes past the bouy the discs act as hydrofoils. those with the convex side down push the buoy down, into the water. Those with the convex side up are lifted up the shaft of the buoy.
Basically, the point is to convert the energy of the water rushing past the buoy into an up and down bobbing of the buoy capturing and dissipating some of the wave or current energy.
Now we are only mitigating a small percentage of the energy but the things are very easy to produce and if made of concrete should last forever. A thick “field” field of them would foul and seriously dampen even powerful waves.
Linked together they would be easy to move as a group and of course might need to be put back in place after storms.
Now, what would the optimum size be? a few really big ones or a lot of little ones?
I also hope people will consider the whole idea of fouling wave energy by converting it into anything else, not necessarily useful but less destructive. Like this idea converts it into the bobbing of the wavebreak