Biofouling or biological fouling is the unwanted accumulation of microorganisms, plants, algae or animals on wetted structures. It is especially significant on boat’s hulls where high levels of fouling have an adverse effect on the performance of the vessel and will undoubtedly increase fuel consumption.

a technique used to combat the growth of marine organisms, such as barnacles, on a ship’s hull. A special coating is applied to the underside of the ship, which needs to be reapplied regularly.

any specially prepared composition used for coating the bottom of a vessel to prevent marine growth Source: Maritime Curators Group: Manual of Curatorship

a type of paint or other coating for the under-water hulls of vessels that is resistant to barnacles, moss, seaweed, Teredo worms, marine grass and various other plant and animal life that would want [..]