Whether you're touching up or tackling a bottom paint job there are a couple of things to consider. Single-Part Polyurethane Paints – Urethane paints are easy to apply, don't cost nearly as much as two-part polyurethanes, and have a long-lasting gloss. Two-Part Polyurethane Paints – Achieve a rich deep shine rivaling the original gel coat, with superior durability. The main difference between marine paints and others is oil content. Oil-based marine paint is most commonly used on the exterior of the boat that is exposed to water.