"Barnacle" has become a term for something tenacious and problematic for a reason--they are determined little buggers that cause lots of damage to marine craft. But dealing with barnacles can create even more problems than it solves.

Biofouling, which occurs when barnacles (or any other clinging species) cover a ship’s hull or anchor line. The U.S. Naval Academy estimates that biofouling creates enough hull-drag to increase the Navy’s petroleum bill by about $250 million every year. For millennia, copper has been used to keep marine life at bay; the Greeks and Romans used copper nails for this reason. The Navy uses it too, mixing powdered copper into boat paint. But as the paint wears, copper seeps into the water, where it has been shown to harm salmon and oysters. And as the paint thins, the barnacles return.