From Pink Tentacle:
Nana, a beluga born at the Port of Nagoya Public Aquarium in July 2007, enjoys creating air bubble rings under water. While it’s not uncommon for belugas to make bubbles by blowing out short puffs of air, Nana has the remarkable ability to suck air bubble rings into the water by swimming near the surface and drawing in big gulps of water. (Go :55 seconds into the video to see this in slow motion.)
I saw Beluga whales at the Georgia Aquarium and they were very cool!