The invention relates to a coating composition comprising a) seawater-hydrolyzable groups covalently linked to a polymer backbone, which seawater-hydrolyzable groups are capable of undergoing hydrolysis or ion-exchange when exposed to sea-water, rendering the polymer partially soluble or dispersible in seawater, and b) zwitterionic groups covalently linked to a polymer backbone wherein the polymer backbones to which the sea-water-hydrolyzable groups and the zwitterionic groups are attached serve as a film-forming binder in the coating composition, and wherein the molar ratio of the seawater-hydrolyzable groups a) to the zwitterionic groups b) is 0.1 or higher. The invention also relates to a method of providing a substrate with anti-fouling performance and to a coated substrate.