Biofouling – the buildup of organisms on surfaces immersed in water – has been a problem for thousands of years. Greeks and Romans covered boat hulls with metal sheathing, nails, pitch, or animal hides to discourage the growth of barnacles, algae, protozoa, and bacteria. Today, the cost to industry due to biofouling is substantial; shipping companies, for instance, spend more than $5 billion annually on this problem. Fouling also harms the environment by increasing drag on ships, so that more fuel is consumed (40–70%), and by introducing invasive species. . .