Amazing Dolphin Video: Playing with bubble rings

Bubble rings are an example of vortex rings. Other vortex rings are smoke rings blown by the experienced smoker.

There are few ways on how bubble rings can be created:

1. Rings can be created by letting air escape through an orifice that is opened and closed abruptly. A bubble-blowing diver falls in this category.
2. Rings can be created by letting a fixed amount of air escape through an orifice that is permanently opened. The bubble machine of David Whiteis falls in this category
3. Dolphins create bubble rings by blowing air in a water vortex ring: by flipping a fin they create a vortex ring of water. The then blow air in the ring, which goes to the center of the vortex ring. In the water vortex ring the natural location of the air is in the center of the vortex. When air and water move in a circular path like they do in the vortex ring, air and water are separated due to the centripetal force. Since density of water is larger than air, water moves at the outside, while the air ends up in the middle.

Sounds like you still don't:

Well you made me curious, that's a kind of thing that would be easy to fake.