Antifouling paint or bottom paint is a type of chemical coating that prevents the attachment and/or growth of marine organisms such as bivalves on boat or ship hulls.
Anti-fouling paint works primarily by poisoning, killing or driving off the free-swimming larva of barnacles and other marine organisms that like to attach themselves (or, in the case of shipworms, bore into) any submerged object, especially wood. Historically, anti-fouling paint has been made of copper and/or tin compounds, and has always been extremely harmful to marine life, sometimes leading to ecological catastrophe, such as one well-known case of mass die-offs at French coastal shellfisheries in the 1970s-80s.
Recently, companies that manufacture anti-fouling paint have been trying to jump on the “green” or “sustainable” bandwagon, but their products are still incredibly harmful. A good rule of thumb is, if a paint or an anti-growth compound warns you against exposing yourself to it, that means it’s also bad for marine life.
The whole sea food chain leans on microorganisms such as plankton and algae. Aside from large marine mammals such as whales, almost every living creature in the sea has a life cycle that involves eggs and tiny swimming larva; to make things worse, many of these young organisms spawn and mature near the shore, in inland waterways, where they can be safe from currents and predators, and often, this is exactly where many boats are docked. If many of these boats sport poisonous bottom paint, the very spawning grounds that sea organisms rely on to nurture their next generation will end up becoming ecological death zones.
Finally, even without environmental considerations, bottom paint can be a pain – it costs thousands of dollars, and takes many hours to apply. The application needs to be done by professionals at a specially equipped boat yard. The boat needs to be lifted clear of water, cleaned off, the areas to be painted need to be sanded and primed before receiving the first toxic coat.
If the application isn’t done properly, the expensive ($250 per gallon) paint can de-laminate and peel off in sheets as soon as you try to use the boat, leaving you in the same situation as before, and many thousands of dollars poorer.
As a matter of fact, you’ll end up poorer regardless, since bottom paint severely degrades the aesthetics of a boat, and can reduce the resale value of a seagoing vehicle by up to a third. It gets worse: even if you’re keeping the boat, it still causes a money drain, because the paint increases water drag, which lowers your top speed and increases fuel consumption correspondingly, by up to 50%.
Yes, bottom paint is a loss all around. Unfortunately, in some cases there’s no good alternative yet – for example, boats that spend a long time traveling in the water (weeks or longer), or very large crafts or ship that can’t feasibly use a Hull Protector may need to be painted. For all other boats, though, the choice is clear: Hull Protector.