A French diver just set a world record for the longest under-ice swim with a 394-foot swim in a frozen lake in Finland

• Arthur Guerin-Boeri on Thursday set a record for the world's longest under-ice swim.
• Guerin-Boeri completed the 120-meter swim in a lake in Finland in three minutes.
• He wore a wetsuit but no flippers, and completed the swim in a single breath.

On Thursday, French diver Arthur Guerin-Boeri set a new world record for the longest under-ice swim.

The diver completed a 120-meter (394 feet) swim in three minutes in Finland's frozen Lake Sonnanen. Guerin-Boeri wore a wetsuit for the swim but no flippers, and completed the swim in a single breath.

"There is fear, anxiety, and it's something I dreaded quite a bit but it was a calculated risk for which I was prepared," the 36-year-old freediver told the Agence France-Press. The freediver spent two hours - first in a sauna, and then doing breathing exercises - preparing for the undertaking.

He posted an 18-minute video to his official Instagram account that shows him prepping for and emerging victorious from the feat. In the video, he can be seen reclining on a wooden chair in full winter gear before the swim and practicing what appears to be breathing techniques while a support crew - including another diver in wetsuit and flippers - waits nearby on the frozen lake.

Wearing a wetsuit and goggles and with a support cable attached to his back, Guerin-Boeri lowered himself into the water through a rectangular hole that had been cut through the ice.

Once underwater, he guided himself forward through the water via a cable. Eight holes, spaced 20 meters apart, were cut through the ice for the swim.

Per an AFP report, Guerin-Boeri plans to try to set another record in a year, at which time he plans to swap out the wetsuit for a bathing suit.

Guerin-Boeri hails from Nice, France, and holds four world records.

The record Guerin-Boeri broke had been recently set: In February, Czech swimmer David Vencl swam nearly 266 feet under ice in two minutes and 42 seconds. Vencl's swim broke a 2017 record set by Denmark's Stig Avall Severinsen's 250-foot under-ice swim.