(CNN) He had swum for 157 days around the entire coastline of Great Britain, but as Ross Edgley approached the finish of his epic adventure, he was energized by something "special" in the water.

He had battled extreme fatigue, cold, pain, jellyfish stings and parts of his tongue falling off during the 1,792-mile journey, but there to greet him on a freezing November morning were 300 swimmers to guide the weary traveler to the shore.

"When I think about it, I can't help but smile," he told CNN Sport. "The best way I can describe it is goosebumps upon tears, upon smiles. Literally, you could feel something in the water. It sounds a bit spiritual but it was just amazing."

Edgley had just become the first person to achieve the epic feat of endurance. Starting on the south coast of England, he was at sea for nearly 23 weeks without once stepping back on land. Come rain or shine, he swam twice a day in six-hour shifts, using lessons he learned while training with the Royal Marines. "Focus on the process and the outcome is inevitable," said the Briton.

Mental resilience

Many told him that he was mad to attempt it. The water was too cold and the tides too strong, they said. For Edgley, though, that was the exact motivation he needed. The 33-year-old thrives off the impossible and the desire to prove everyone wrong. "I knew how to put one arm in front of the other," he joked. "It's just the case of doing that until you got all around the coast." Meeting in London, Edgley somehow retained an impressive level of vigor just days after completing the mammoth challenge. He even had an infectious enthusiasm for his multiple media commitments, treating them as therapy for the hardship that he tried to block out over the summer. It was this positive attitude to life combined with a "feral" ability to keep putting his face back into the freezing cold water that made it possible.

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Just like his physical prowess, Edgley's mental resilience has been refined over the years. He graduated with a 1st class honors degree from Loughborough University School of Sport and Exercise Science and has continued his fascination with sports psychology ever since. The theories he learned enabled him to ignore the "physiological hand-brake" when his mind would tell his body to stop. "I was in pieces but I thought, 'Are you actually completely fatigued, or is that you just trying to pull that physiological handbrake? Have you got any more?,'" he said.

Are you completely fatigued, or are you just trying to pull that physiological handbrake?

'Eccentric explorer'

Unsurprisingly, Edgley comes from an active family. His mother was a sprinter, his father a tennis coach, one grandfather a marathon runner and the other in the military. Sport was all they would talk about over dinner, and Edgley developed a fascination for fitness and mammoth tests of endurance. Before this swim, Edgley had climbed a rope to the height of Everest, run a marathon while pulling a car and completed a triathlon whilst carrying a 100-pound tree. Some of his motivation stems from a desire to emulate a previous British explorers.

Captain Matthew Webb, who in 1875 became the first man to swim across the English Channel, is a particular source of inspiration. Like Edgley and the Great British Swim, everyone told Captain Webb that swimming the Channel was impossible. "There was something about that which was so amazing, so British," he said. "This eccentric explorer, I loved it."

Edgley was joined by 300 swimmers for the final mile of his epic around-Britain swim.

The darkest moments

Edgley was accompanied on his odyssey by husband and wife duo Matt and Suzanne Knight. Their boat was the support vehicle where Edgley rested, ate and slept when not in the water. Swimming, as they all found out, was just a small part of the expedition.

The stories Edgley tells of extreme cold, sleep deprivation and wet-suit chaffing (so bad that his open wounds stuck to his bed sheets) instead defined his swim. There was one particular run-in with mother nature that really stood out. While navigating the Gulf of Corryvreckan in Scotland -- home to the third largest whirlpool in the world -- Edgley was hit in the face by a jellyfish. This was nothing new. Edgley was stung 37 times during the journey but this sting felt "a little different," he said. "It just didn't go away, it was searing into my skin."

After hours of swimming through excruciating pain, Edgley identified the root of the problem. He found the tentacle, which had applied the first sting, threaded through his goggles. It had been slapping him in the face for hours, causing multiple stings to his left eye. "The goggles wouldn't fit back on my face because my left eye was so swollen," Edgley laughed. "I had to just punch the goggles into my face so that they no longer leaked and then I could carry on swimming."

Edgley fashioned a makeshift anti-jellyfish mask.

It's just one of the nightmarish scenarios that Edgley could not prepare for. His training, nevertheless, was brutal. Having previously written "The Word's Fittest Book," Edgley wanted to put his theories to the test. The hours spent in the gym, swimming pool and the open water were all informed by the multiple endurance events he'd previously completed. He developed the concept of work capacity -- which considered how much his body could take and still recover from. After pushing this boundary to its absolute limit, it became evident that the Great British Swim could, on paper, be possible. That small glimmer was enough.

It was as much an exploration of my digestive system as it was the British coastline.

Edgley consumed up to 15,000 calories every day.

Eating with an eroded tongue

Food was also a vital component of the mission. A diet plan had been carefully created prior to the start but it didn't last long. Instead, it was a diet of necessity. Edgley consumed between 10,000-15,000 calories a day to meet the energy requirements of his body. The method would often throw up some unlikely combinations, such as a feast of two-deep fried pizzas and a super-healthy green shake. "I call it edible exploration, it's whatever works for me. It was as much an exploration of my digestive system as it was the British coastline," he said. There was also the surprising problem with palatability. After weeks of swimming 12 hours a day, Edgley developed salt-tongue which made eating certain foods "taste like sandpaper." It's a condition caused by sea water which erodes the tissue and causes part of the tongue to fall off (it has since grown back). Bananas were sometimes the only thing Edgley could cope. He consumed a remarkable 649 bananas, recording each on the cabin roof.

Edgley records each banana he eats on the cabin roof.

Getting back on land, my feet are like, 'What are you doing? They are still struggling to figure out what's going on.

His physique has changed a lot since the start of the swim, when he had a body sculptured by hard work in the gym. He has added 10kg of "seal blubber" to his upper body, and is now learning to walk properly again after "skipping leg day" for almost half a year. A lack of walking has caused the arches of his feet to sink. "Getting back on land, my feet are like, 'What are you doing? They are still struggling to figure out what's going on,'" he said. The fitness expert is proud of his new physique, though, and hopes to encourage others to be "instruments not ornaments," an indication of how he views an aesthetics-driven fitness industry.

What next?

Despite the obvious hardship, Edgley looks back positively on the experience and insists that he's not yet bored of swimming. "The sunsets, swimming with minke whales and dolphins. For all of the hardship which is easy to talk about, there were so many privileges as well," he said. Edgley has promised his family some time off before embarking on his next challenge. "If you can swim around Great Britain, where else can you swim to?" he teased. "I'll have my Christmas dinner and then maybe next year."