Spray Nine's Boat Bottom Cleaner has been judged to be the "Best Choice" as well as the "Budget Buy" in its ability to clean those dreaded water line stains. This non-abrasive cleaner is a gel designed for clinging to the hull and digging into those stubborn areas. Holds tight to many surfaces including fiberglass, wood, plastic, and metals! It's the MyBoatStore selection for taking the guess-work of of what is often one of a boat owners most dubious tasks!