Yes, as Terry said, paint will only protect the buoy for a certain period if time, before barnacles and other marine life start to cling to it, and strip the paint off. Gradual errosion caused by the waves/tide/bottoming out on sand dosen't do the buoy any favours either. But anyway, as far as I'm aware, they last a good length of time though with care and attention, or am I wrong Terry?
Jack.