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, algae, and waterline discoloration from marine stains. It attacks, loosens, and removes Zebra mussels and barnacles from hulls, exposed power drives and propellers. Use pre-season, for winterizing, or anytime boat is removed from water for scheduled maintenance. Sold in Case Quantity only. Gallons truck ship only.