Abstract: A floatable barrier for retaining substances in the water within an area defined by the barrier, comprises an elongate body formed of vinyl or resilient polymeric material, the elongate body bendable in a loop shape to retain the substances within in the loop, the elongate body including two or more elongate sections connected side by side, one section being a lower section having elongate cavity area for filling water therein, and another section being an upper section extending upwards to a height from the lower section, the upper section having elongate cavity area for filling air therein. The floatable barrier can further comprise an intermediate section having elongate cavity area for use as a channel for transporting and discharging the oil or liquid substance through the channel. The barrier can be used for various purposes such as for cleaning oil spill, for retaining pollutant materials therein, and for cultivating marine products therein.