I can think of two good reasons to use biodegradable boat soaps versus harsher formulas such as dishwashing detergents that contain phosphates and other harmful chemicals. Eco-friendliness ranks high on the list, plus these soaps are also gentler on common boat surfaces such as gelcoat, canvas, carpet, clear enclosures, vinyl, high-density plastics and your boat’s wax finish. But do they actually clean? To find out, we tested three bio-d soaps on the gelcoat of a boat left with a gnarly mess after two days of ocean fishing.