Bubble-feeding - "Humpbacks cooperate in hunting and have developed a method of rounding up highly concentrated masses of prey that is called bubble-net feeding. The hunting members of a pod form a circle 10-100 feet (3.1-31 m) across and about 50 feet (15 m) under the water. Then the humpbacks blow a wall of bubbles as they swim to the surface in a spiral path. The cylindrical wall of bubbles makes the trapped krill, plankton, and/or small fish move to the surface of the water in a giant, concentrated mass. The humpbacks then eat a large, hearty meal. "

Masaki