So very cool. Thanks!

Not just bubbles... bubble rings! That's awesome!

So cool, bearwife! More on the phenomenon from Snopes, and they include a quote from a 2000 paper: "Bubble Ring Play of Bottlenose Dolphins: Implications for Cognition," published in the Journal of Comparative Psychology:

Air-breathing dolphins always produce bubbles when they expel air underwater. Besides bubble rings, dolphins also produce a wide variety of other bubble types. They occasionally emit bubble streams concurrent with vocal activity. When surprised, curious, or excited, dolphins often emit a rapid exhalation termed a bubble burst. Breathing in dolphins, unlike in other mammals, is solely under voluntary control, a crucial feature in their adaptation to a fully aquatic existence. Whereas the physics of ring formation is straightforward, the actual production of stable rings may require some practice, expertise, and forethought by the dolphins.

That is so fun! I love watching them playing with the rings!