Remove boat from water. Allow deposits and stains to dry thoroughly. Stains and deposits found above the waterline may be removed while boat is in water. Apply product to the dry surface of hull using a sponge, roller or brush. Keep deposits and stains wet and foaming with the product. Re-apply product to maintain foaming action; after 10 minutes of foaming action, most surfaces should be clean and ready for rinsing with water. Heavy deposits may require an additional application and light scraping. Avoid contact with boat trailers. Wash any spills or drips immediately.