Ross Whales creating a toroidal vortex.
While this still image of Ross Whales youtube video does not display the same level of beauty other flow vis images posess, the physics of the toroidal vortex is simply amazing. The vortex ring is a rotating fluid (in this case air that came from the divers lungs) that moves through the ocean to the surface, which results in the donut ring shown. With air being less dense than the water, the air bubble is pushed to the surface.
Ross Whales has done an incredible job photographing this phenomenon, however I believe the true beauty of the toroidal vortex has yet to be photographed. Especially with the fact that some dolphins & whales have the natural ability of making these vortexes. There are videos on the web of dolphins playing with their own toroidal vortex.