Bubble rings, or dolphin rings or toroidal vortex rings, are cool circles of air that travel through the water sort of like smoke rings in the air. This fellow at Cornell has figured out how to create dolphin rings in the water and in this video he shows you how to do it.
OK, it's all wonderful that this guy can make those ring, but did you see what the dolphins were doing? No really... did you see that? Wow! I've never seen anything like it! Here's another video on the phenomenon.
Apparently it's not just dolphins that make these and they aren't only in the water. Bubble rings can be found in more places than you might expect. Color me amazed.