Rust-Oleum® Marine Coatings Boat Bottom Antifouling Paint is a hard, smooth protective coating designed to prevent the buildup of barnacles, algae, and other marine growth on boats. Ideal for use below the waterline, this specialized paint contains copper that is gradually released to provide lasting antifouling protection. Suitable for both freshwater and saltwater environments with mild to moderate fouling conditions, it ensures your vessel remains clean and efficient in the water.