Novice here - isn't there some static hull shape that would react to waves and result in motion, much like those plastic widgets that spin only in one direction?
This design is capturing energy from the vertical vector of wave's motion, so it works regardless of the direction of the wave or the boat. Capturing the horizontal part of the wave would be possible, but only if you wanted your boat to travel in the same direction and at the same speed as the wave. That's not so useful.
You can capture wave motion in all directions with a pendulum based design like this: