National Geographic biologist Lisa Kelly is no stranger to Antarctic Diving – she learned to dive in these cold waters, and takes every chance she can to drop in below the ice. But last September, in the green haze of a plankton bloom, Kelly found herself face to face with an animal she'd never encountered before: a 13-foot leopard seal. 

Even for an experienced diver like Kelly, the encounter sparked mixed emotions. Leopard seals are extremely effective predators, boasting powerful jaws, large reptile-like heads and a flexible neck that allows them it to pull their heads backwards before striking prey – much like a snake would. "I backed myself up against a cliff," she recalls. "But it was like she was playing, she was certainly not aggressive – but very, very curious."

For the next 20 minutes, Kelly inched her way back to the surface, with her new acquaintance  following her all the while. "I've got the camera in front of me and she is right there, she comes in – directly up to to it, checking herself out in the reflection ... It went on like this – me scurrying up five to ten feet and the seal coming back in. She actually followed the zodiac [the inflatable boat] back to the ship. It was that moment that I fell in love with leopard seals – with their power and their grace."

Top header image: Christopher Michel/Flickr