Moments before setting a national freediving record in April, Lt. Col. Laurence Paik checked to make sure his nose clip was fastened, his flashlight was beaming, and his lanyard -- attached to a line plunging deep into the Mexican cenote, or freshwater sinkhole -- was secured.
The check was akin to the rigid pre-flight procedures Paik had learned as a Harrier pilot in the Marine Corps. Now, it is part of a critical routine he uses to prepare for diving into some of the most extreme depths the human body can endure.
Paik competed under the International Association for Development of Apnea, or AIDA -- a French-born organization that has judged freediving records since its founding in 1992. When he arrived at the Xibalba Freediving competition in Mexico, his intent was to beat the "constant weight, no fins," or CNF, record of 72 meters.
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That category of freediving is considered the most challenging because it requires the swimmer to dive without the assistance of fins -- just pure swimming and one allotted hold at the bottom of a safety rope that marks the transition between descent and ascent.
Paik, who is assigned as a reserve intelligence and foreign area officer with the Marine Innovation Unit, beat that record on April 20, according to the AIDA, by diving 73 meters into the sinkhole and carefully breaststroking back to the top.
At the surface, he had to verbally tell the judges he was OK and give a hand signal, a requirement for a successful dive to ensure that he did not pass out. Paik brandished the tag that he collected at the bottom of the line, showing that he completed the record.
"It was -- in some way -- a relief," Paik told Military.com in a recent interview. "I knew that this was going to be my last opportunity in that competition. ... It was a validation of the work and effort and the confidence that I had built in the preparation and all the training."
Paik had made an initial attempt earlier that week, but was unsuccessful. He had hit the 73-meter mark but had a "surface blackout" at the top of the dive -- passing out due to a trick of the light that made him feel closer to air than he thought.
"I actually hit the light and thought I was close to the surface and started my stretch as if I was going to be breaking the surface shortly thereafter," he said. "But that's when I realized it wasn't as close as I thought."
He reset. He reviewed safety camera footage and data from the dive computer that helps track his depth and progress. He adjusted his initial dive into the water so he didn't splash as much, a move that helped retain energy and efficiency needed for the descent.
On the way down, the chasm looks endless. Shimmering streaks of light from the sun above beam down, giving the cave an ethereal look not unlike science-fiction depictions of warp speed.
At greater depths, pressure builds to the point where a human being's lungs can shrink to the size of fists and dangerous levels of nitrogen can build up in the body, leading to nitrogen narcosis, or "rapture of the deep," as it is known in diving circles.
"There becomes a point where your lungs are at their minimum volume, and they basically won't get any smaller," Paik said. "So, what you have to do is take some air from your lungs before that point and store it ... in your neck, in your cheeks, in your mouth."
As he descends, he uses some of that air to "equalize" the pressure building in his ear canals.
"That's one of the equalizers," he said of the sport. "If you can be really good at equalization, then you can get to your physical potential. But if you don't have that equalization, then you might be an incredible athlete, but not be able to reach that potential."
On the other side of that danger lies what Paik described as euphoria. That "rapture of the deep" brought on in part by oxygen depletion and nitrogen has led to what freedivers have described as a feeling of elation, which Paik said is part of the thrall over diving.
A longtime competitive swimmer, Paik started freediving in 2019. He said that he fell in love with the sport through spearfishing where he felt unburdened by the noise, bubbles and weighty gear that comes with scuba diving.
Off an island in Bali, Indonesia, Paik got his first taste of pure freediving. He explored the wreck of the U.S. Army Transport Ship Liberty, which was torpedoed by the Japanese military during World War II.
"I had already scuba dived that same wreck," he said. "Now, freediving the same wreck was a completely different experience -- you don't have the valves and the bubbles and the noise. ... Now, I've basically got comparatively very little equipment. I can go vertical, I can do all sorts of maneuvers, and I can get really close to all that sea life."
From there, he fell in love with the freediving community. A niche group, he said that the community itself "is one of the most attractive and fun things about freediving," with a camaraderie built around an intense, sometimes dangerous activity.
Since Bali, Paik has freedived in only three competitions, one of which where he broke the national record. While he's been a lifelong swimmer, getting time "in depth," as he called it, can be a challenge, especially as he lives on the East Coast, where deepwater sinkholes like the one in Mexico are few and far between.
He said that once the equalization piece of the puzzle is mastered, most freediving training can be done on land. He trains with conditioning, stretching and breathing exercises. He spends a lot of time in the pool, swimming in preparation for this record in particular.
Paik attributes some of his freediving success to his Marine Corps experience. He joined the service in 2005 through the Reserve Officers' Training Corps, or ROTC. After basic officer training, he received an air contract, meaning that he would be put in an aviation role, which is where he says he got the "checklist mindset" he employs in the water.
He spent 12 years on active duty before switching to the reserve, where he now serves with the Marine Innovation Unit as a defense engagement manager, connecting different parts of the Marine Corps and the Defense Department to "advance technology adoption," Paik said.
"With my swimming background, with my aviation background in terms of being put into different kinds of environments and being asked to perform, I was kind of already used to a lot of the things associated with freediving," he said. "So, it was just a matter of putting them all together."
Paik intends to continue competing, potentially for another CNF record, he told Military.com.
"I think 80 meters would be doable," he said. "The world record is 102 meters. It's nice to think that maybe one day that's in the realm of possibility," adding that it would take a concerted effort to get to 80 meters.
"Regardless of whether I can do that kind of stuff, the activity itself is rewarding," he said. "There's plenty more that I have yet to explore in Asia and Europe and the Middle East -- so there's a lot more left to do."
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