Provided is a room temperature-curable organopolysiloxane composition for preventing aquatic organisms from adhering to and growing on an underwater structure. The composition comprises: (A) an organopolysiloxane represented by the following general formula (1) wherein R1 represents either a hydrogen atom or a monovalent hydrocarbon group that may have a substituent group, and n represents an integer of not smaller than 1; (B) a hydrolyzable organosilicon compound and/or a partial hydrolysis condensate thereof, represented by the following general formula (2) wherein R1 represents either a hydrogen atom or a monovalent hydrocarbon group that may have a substituent group, R2 represents either an alkyl group that may have a substituent group or a cycloalkyl group, and a represents an integer of 1 to 3; (C) a curing catalyst; and (G) a bleed oil.