A friend sent me this text an video, so I'm not sure of the author. I've not seen this particular playful behavior before. I have seen both dolphins and whales create 'bubble corrals' to entrap schools of fish.
Just another of many indications of their advanced intelligence.
"I HOPE YOU LIKE THIS - IT IS BEAUTIFUL! I CAN'T SPEAK FOR THE
The attached video is of dolphins playing with silver colored rings
which they have the ability to make under water to play with. It isn't
known how they learn this, or if it's an inbred ability.
As if by magic the dolphin does a quick flip of its head and a silver
ring appears in front of its pointed beak. The ring is a solid, donut
shaped bubble about 2-ft across, yet it doesn't rise to the surface of the
water! It stands upright in the water like a magic doorway to an unseen
dimension. The dolphin then pulls a small silver donut from the larger
one. Looking at the twisting ring for one last time a bite is taken
from it, causing the small ring to collapse into a thousands of tiny
bubbles which head upward towards the water's surface. After a few
moments the dolphin creates another ring to play with. There also
seems to be a separate mechanism for producing small rings, which a
dolphin can accomplish by a quick flip of its head.
An explanation of how dolphins make these silver rings is that they
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."