Das ist so schön. Delfine, die unter Wasser mit selbst gemachten Luftblasen spielen. Mehr über dieses Phänomen und die Physik dahinter gibt es hier zu lesen (*.pdf Datei):
Any spherical bigger than about two centimeters in diameter will quickly become a ring because of the difference in water pressure above and below the bubble. Water pressure increases with depth, so the bottom of the bubble experiences a higher pressure than the top does. The pressure from below overcomes the surface tension of the sphere, punching a hole in the center to create a doughnut shape. As water rushes through the hole, a vortex forms around the bubble. Any vortex ring travels in the same direction as the flow through its center; in the case of these simple air rings, the vortex flow, in combination with the air’s natural buoyancy, propels the bubbles toward the surface.
(Video Direktlink – via reddit)
P.S. Machen Delfine übrigens auch im offenen Meer.