Lewis Pugh, an activist swimmer who regularly braves the world's frigid waters to draw attention to environmental issues, has once again made history. The 45-year-old earlier this month completed a series of five swims in the Ross Sea off Antarctica wearing nothing but a Speedo, bathing cap and goggles. The water temperature? A mind-numbing 28-30 degrees Fahrenheit, with an air temperature of minus 25 F and wind gusts in excess of 45 miles per hour.

" 'Cold' is a word that holds no meaning in a blizzard in the Antarctic Ocean. It was very difficult to breathe. I was gasping for air. I kept telling myself to keep calm. I’ve never experienced anything like it," Pugh told National Geographic.

Having survived his latest challenge, Pugh now holds the world record for the farthest south swim ever made by a human. Such accolades, however, are secondary to the real reasons behind his being there in the first place.

"Very few people have ever heard of the Ross Sea," he told NatGeo. "It’s in the most remote part of the world. And no one lives there, other than a few scientists. How do you draw attention to such an important wilderness area, which is being heavily impacted by industrial fishing and climate change? Especially when the media is saturated with news of civil wars, famines, genocides, financial crises, and the like. Swimming in a Speedo in Antarctica captures the media’s attention like nothing else. And the public can relate to my commitment to the cause."

Before any other activists consider making plans for their own cold-water attempts, keep in mind that what Pugh can do is completely out of the ordinary.

"My core body temperature rises from 37°C to 38.2°C before I get into freezing water," he writes on his site. "That does not sound like a lot, but if your core body temperature rises more than 2°C you are clinically hyperthermic. Drop 2°C and you are clinically hypothermic. So being able to raise my core body temperature by 1.2°C makes an enormous difference. It enables me to stay in freezing water for prolonged periods of time."

Pugh's ability has been observed first-hand by sports scientist Tim Noakes, who coined the phrase "anticipatory thermo-genesis" to describe the process. Before hitting the frigid water, Pugh generally meditates for 15 minutes to music (Verdi's "Chorus of the Hebrew Slaves" is one of his favorites), building his heart rate from 70 to 160 beats per minute. It's a technique he's honed over the years, telling CNN in 2009 that he generally swims in cold water for one hour a day, followed by four hours of meditation.

While Pugh claims his ability is unique, Tibetan nuns would claim otherwise. In 2013, a team of researchers at the National University of Singapore found that a form of meditation used by the nuns called g-tummo allowed them to raise their core body temperatures to 38.3 degrees Celsius.

"The participants whom I taught this technique to were able to elevate their body temperature, within limits, and reported feeling more energised and focused," researcher and associate professor Maria Kozhevnikov reported in the study. "With further research, non-Tibetan meditators could use 'vase breathing' to improve their health and regulate cognitive performance."

Check out a video on Pugh's record-breaking five swims' challenge below.

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Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

How Lewis Pugh survived a frigid swim in Antarctica
World's leading cold-water swimmer can mentally raise his core body temperature 100.4 degrees, a phenomenon called 'anticipatory thermo-genesis.'