The absence of any external pumps, suggests to me that there...

The absence of any external pumps, suggests to me that there will be minimal movement of the buoy in an up and down direction.

It looks to be that the lever action of the pink coloured couplings on each tether are designed to capture all sideways movement regardless of which way the buoy is moving.

Each tether will have a different directional force acting on it at any given time. The addition of extra tethers would further increase energy harvesting capacity.

My head is starting to spin, when I think of how researchers will be able to calculate what this does to output.