And Tinkerbell proved able to create a silver helix, spiraling perhaps 20 feet long, that would spring into life in a fraction of a second and remain stable in the water as she swam past, observing it with sonar and vision. This was a wonderful mystery to ponder. 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 the dolphins break the line, the ends are drawn together into closed rings. Owing to the Bernoulli effect, 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.
There also seems to be a separate mechanism for producing small rings, which a dolphin can accomplish by a quick flip of its head. There is little doubt that this is what is occurring. However, understanding the physics should not diminish our appreciation of this spontaneous act of creation by a dolphin mind. These young dolphins have detected, understood, and manipulated a subtle aspect of their environment, for no reason other than play. Creation of these rings by dolphins isn't new.