Thats actually a real phenomenon in RL.
A herd of whales (humpbacks, mostly) find a school of fish. they Then circle underneath them, blowing bubbles. The bubbles act like kind of a wall, and the whales make increasingly tigher rings until the fish are forced into a very tight pack.
Then the whales dive, and rise up from under the fish with their mouths wide open - getting huge mouthfuls of fishy fun. They generally surface all at the same time, and it looks exactly like that.