A pneumatic plunger system for use in a commercial seine fishing vessel, comprising apparatus for expelling a mixture of forced air and water through a plurality of nozzles that are located along the keel of the vessel. The forced air and water which is ejected through the nozzles creates a wall of air bubbles extending substantially vertically and downward from the keel. Fish swimming between the net and the wall of air bubbles are startled by the air bubbles and are repelled into the net.