The invention relates to the use of a polymer including salts of amine-functional groups and/or salts of phosphine-functional groups bound (pendant) to the backbone of the polymer, said salts including as counter-ion the anionic residue of an acid having an aliphatic, aromatic, or alkaryl hydrocarbon group comprising at least 5 carbon atoms in antifouling compositions. The invention further relates to antifouling compositions including such a polymer.