Schooling fish, a mesmerizing, undulating mass of sleek bodies that bends, breaks and becomes again. This collective movement is dazzling, but also puzzling. A clear understanding of how and why it happens has been hard to come by. But we’re slowly unraveling the mystery behind it all.

Why do fish school or swarm? And how do they shift in unison? This Hakai Institute video introduces what we know about the biology and behaviors of these stunning displays.

Follow this intro with Secrets of Schooling: Investigating the collective behavior of fish.

Then watch these videos about fish swarms: Underwater Bigeye trevally fish tornado in Baja California Sur, Predators Attack Fish Bait Ball, and a seal herds fish off the coast of Australia’s Bondi Beach.