Bottom paint is applied below the waterline on your boat, and typically refers to antifouling paint that prevents marine growth from clinging to your hull. Antifouling paint forbids aquatic growth such as barnacles, mussels, and sometimes oysters, and plant growth from attaching to your trawler. Most antifouling paints use the diffusion of metallic elements within the paint to halt these foul critters from bonding. For more details, visit underwaterdivingtechniques.blogspot.com/2021/08/how-to-choose-best-bottom-paint-for.html