Keep your boat free from the buildup of barnacles, algae and other marine growth with Rust-Oleum Marine Coatings Boat Bottom Antifouling Paint. This marine coating is a hard protective antifouling paint that can be applied over most aged hard antifouling coatings. It can be applied on fiberglass boats with outboards or outdrives with no danger of electrolysis, provided the drive units are not coated.