Dolphins play frisbee with bubble rings.

This suggests that they understand both play, and fluid dynamics. After first creating invisible vortices in the water with their tailfins, these dolphins - particularly children - then infuse the vortices with air from of their blowhole. The result are called air-core vortex rings, and can be up to two feet in diameter.

The invisible dance of physics keeps the ring from going anywhere, at least for about ten seconds. But that is long enough for some playful porpoises to nudge the ring along wherever they like, and admire their handiwork. When they’re finished with their liquid toy, they bite it, and it breaks into thousands of tiny bubbles that, far more predictably, float to the surface.

They can also create helices up to twenty feet long. The same rules apply.

Ring-blowing stops entirely when children are outnumbered by adults. Which suggests the worrisome possibility that all species eventually grow up to be killjoys.