Pictures: Mysterious Deep-Sea Life Below Antarctica

In the deepest dive ever beneath Antarctic ice, thriving plants and animals are captured on camera.

In an expedition unlike any other, National Geographic photographer Laurent Ballesta took a cold, harsh plunge below the sea ice in the deepest dive ever under Antarctica.

In October 2015, the beginning of spring in the southern hemisphere, Ballesta joined a small team for a 36-day excursion beginning at the Dumont d’Urville, the French scientific base on the Adélie Coast of East Antarctica. The trek took place as ice began to break up, allowing Ballesta and his team to break through 10-foot-thick ice and dive down as deep as 230 feet.

Ballesta, who’s worked for decades as a deep-diving photographer, previously dived to 400 feet off South Africa to photograph rare coelacanths, and in French Polynesia, he dived for 24 straight hours to document the mating of 17,000 groupers. (Read "800-Pound Groupers Making a Comeback—But Not Everyone's Happy")

The process for this journey wasn’t a simple one, however; the trip took two years to prepare.

Once in Antarctica, getting into the diving suits took an hour alone, and once equipment was secured, divers carried up to 200 pounds below the ice. The weight makes swimming almost impossible, Ballesta says, but without dry suits, divers would die in as little as 10 minutes.

The five-hour dives into the sub-29 degrees Fahrenheit water—salt water remains liquid below freshwater’s freezing point of 32 degrees—are excruciatingly painful.

But what Ballesta captured on the ocean floor, he compared to “a luxuriant garden.”

“The waters under Antarctic ice are like Mount Everest: magical, but so hostile that you have to be sure of your desire before you go,” he said.

At depths of 30 to 50 feet, forests of kelp, giant sea stars, and giant sea spiders are visible to the naked eye and much bigger than those in warmer waters. (Read "This Extreme Swimmer Fights for Antarctica's Oceans—in a Speedo")

At 230 feet, the limit of the dives, Ballesta says the diversity is greatest. Gorgonian sea fans, shellfish, soft corals, sponges, and small fishes exhibit the “colors and exuberance” like that of tropical coral reefs.

Once above the ice, Ballesta says it took seven months after returning to Europe for his damaged nerves to recover from the harsh conditions he experienced in the icy waters.

Although the trip was intense, it was well worth it, according to Ballesta.

“You cannot go half-heartedly; you cannot feign your passion. The demands are too great,” he said. “But that’s what makes the images you see here unprecedented, and the experience of having taken them and of having seen this place so unforgettable.”

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Related: These Weird, Wondrous Animals Live Under Greenland's Ice Caps

A diver captured stunning video of the unique marine life that lives in the cold waters underneath the ice caps of Tasiilaq, Greenland.