Professional Boat Hull Cleaner is the choice of marinas and serious boat owners for hull cleaning during the season as well as winterizing afterward. ZING® Professional Boat Hull Cleaner is a heavy duty professional strength formulation that easily and quickly removes the toughest build-ups on fiberglass, painted wood and steel hulls. Use in fresh water and salt water. Cleans scum, waterline discoloration and stubborn stains and residue from algae, barnacles, and zebra mussels on hulls, exposed power drives and propellers. Use pre-season, for winterizing or anytime the boat is removed from the water for scheduled maintenance.