The buoy will be moved by the force exerted on it by the waves.
Step-by-step explanation
As the buoy is anchored to the ocean floor, the buoy will be floating in the ocean floor.
When the large wave approaches, it will act as an external unbalanced force on the buoy.
The waves will consist of crest and trough.
The crest region have higher force. So the crest will first interact with the buoy and the external force of crest will make the buoy to float upward along with the motion of crest.
Then the trough region will lessen the force and thus it will again come back in its original position.