A group of whales swims in a shrinking circle blowing bubbles below a school of prey. the shrinking ring of bubbles encircles the school and confines it in an ever-smaller cylinder. the whales then suddenly swim upward through the bubble net, mouths agape, swallowing thousands of fish in one gulp. this ring can begin at up to 30 metres (98 ft) in diameter via the cooperation of a dozen animals. some of the whales blow the bubbles, some dive deeper to drive fish toward the surface, and others herd other fish into the net by vocalizing. humpbacks have been observed bubblenet feeding alone as well.