coatings formed from materials including acrylate and methacrylate polymers and copolymers the vinyl polymers including polyvinyl chloride polyvinyl acetate polyvinyl butyral polyvinyl chloride acetate vinyl chloride vinylidine chloride copolymers the polyethylene polymers including polyethylene polyhalogenated ethylenes polystyrene and the styrenated alkyds further coating materials include thermosetting as well as other thermoplastic materials illustrative of such materials are the alkyd resins including the modified alkyds and the terpenic and maleic alkyds the amino resins including urea formaldehyde and melamine formaldehyde the protein plastics including casein zein keratin peanut and soy bean plastics the cellulosics including cellulose acetate cellulose nitrate cellulose acetate butyrate regenerated cellulose lignocellulose ethyl cellulose hydroxyethyl cellulose and carboxymethyl cellulose the epoxy resins the ethylene and fluoroethylene polymers the furan resins the polyamides the phenolics including phenol formaldehyde phenol furfural and resorcinol formaldehyde the polyester resins including the saturated polyesters the unsaturated polyesters and the polyfunctional unsaturated esters and the silicones the microbiocidal additive of the present invention can be mixed in accordance with the present invention with paint or other coatings and applied to underwater surfaces to inhibit the growth of marine organisms such as algae on such coated surfaces for example the microbiocidal additive of the present invention can be incorporated into paint and painted on a boat bottom the treated coating will inhibit the growth of algae and other marine organisms on the bottom of the boat in addition the microbiocidal additive can be incorporated into a material that is to be immersed in water for long periods of time to inhibit the growth of algae on the material an example of such use for the microbiocidal additive of the present invention is incorporating the microbiocidal additive of the present invention into fiberglass that is to be used to mold a boat.