Dolphin Play Bubble Rings
According to the quote reproduced on the Projo's Subterranean News:
A physicist would marvel at some of the play behavior observed in young dolphins at the Project Delphis laboratory. They blow underwater bubble rings by injecting air into water vortices, about the thickness of a straw and 1 to 2 feet in diameter. The rings don't rise to the surface! The babies play with these underwater toys by moving them around with their rostrum, or biting them. They even bounce the rings off the wall, and elongate them with a flick of their dorsal fins into 15 foot corkscrews.
Well I don't know if any of this is interesting physics-wise, but physicists certainly would marvel at it, since it is amazing.