The article deals with the antifouling resistance in the fresh water of the protective coatings based on the ship paint XC-413 containing 5% of hydrophobic cationic biocide 1,3-didodecylimidazolium tetra fluoroborate (DD1M-BF4). The biocidal additive was found to have high leaching resistance off the coating and improve its hydrophobicity. After 228 days exposure in the Dnipro River the fouling biomass was formed mainly by the Dreissena polymorpha (92.5%). The surface of DD1M-BF4-modified coatings showed more than twenty time reducing of total biomass comparatively to control substrates. The obtained results showed the considered cationic biocides to be promising antifouling additives for industrial stains, used for protection of the underwater construction and vessels.