The Amazing Dolphin Trick

We all knew dolphins are playful, but blowing bubbles? And then turning those bubbles into spinning rings? See the footage below:


And here's an explanation someone sent, "these silver rings...are 'air-core vortex rings'. Invisible, spinning vortices in the water are generated from the tip of a dolphin's dorsal fin when it is moving rapidly and turning. When dolphins break the line, the ends are drawn together into a closed ring. The higher velocity fluid around the core of the vortex is at a lower pressure than the fluid circulating farther away. Air is injected into the rings via bubbles released from the dolphin's blowhole. The energy of the water vortex is enough to keep the bubbles from rising for a reasonably few seconds of play time."