By Don Riddell, CNN

(CNN) -- It was a tiny error in judgement, but within seconds he realized that the consequences could be potentially life threatening.

"That wave sucked me up into the mouth of it and slammed me onto a rock and just absolutely destroyed me," American surfer Billy Kemper tells CNN Sport.

"Knocked me out unconscious. Collapsed my lung. My pelvis was broken down the middle, I had to get my knee reconstructed, the injury-list goes on and on," adds the 30-year-old surfer as he details the impact on his body. "It was straight up life or death."

Kemper says there was a brief moment of calm before the impact last year, a period of peace inside the wave, when he couldn't even tell which way was up. And then, the visceral experience of life's fragility.

"I was just hyperventilating and blacking out through the pain, you can't forget pain that much."

Surfing 'Jaws'

Kemper says that he never feared the waves: "I was on a surfboard months before I could walk, I was basically, you know, born into the ocean."

As the nephew of the big-wave surfing icon Laird Hamilton and growing up on Maui, Hawaii's second largest island, surfing has always been in Kemper's blood.

"Part of the culture of being raised in Hawaii and being raised on rock surrounded by ocean is that there's never a fear."

While some people might develop their love for a team or a sport by being taken to a game at an early age, Kemper's equivalent of The Staples Center or the Los Angeles Lakers was geologically sculpted and just a couple of miles away.

The most feared wave in the world, towering at up to 60 feet and known as "Jaws," because it resembles the mouth of a shark, was practically on his doorstep.

"We would watch it like a kid watching The Lakers," he said.

Comparing himself to a young fan hoping to get his basketball signed by Kobe Bryant, there Kemper was, with his surfboard, making plans for the rest of his life.

"'Mom, Dad'," he'd say, "One day I'm going to surf 'Jaws.' And they just laugh at me, like 'yeah right.'"

He was serious though; now aged 30, Kemper is regarded by many as the best big-wave surfer in the world. According to the World Surf League CEO Erik Logan "he consistently pushes the realm of what is possible in his continuous pursuit to travel to the world in search of the most ferocious storms and biggest waves."

Among numerous other accolades, Kemper is the 2018 big-wave world champion and a four-time "Jaws" event winner, considered the most prestigious prize in the sport.

He's an accomplished surfer at every level, but he's a rare breed of surfers -- around a dozen of them -- who eschew the speed, precision and creativity of the regular WSL Tour for the blood and thunder of the biggest waves on the planet.

"Billy's accomplishments as a professional surfer indisputably show he is one of the world's best big-wave surfers," adds Logan.

When asked to describe the feeling of standing on top of a mountainous wall of water, Kemper compares it to looking out of the window of an eighth-floor apartment. He struggles to articulate the feeling without using an expletive.

"I don't know exactly what words I'd put it into that would be good for camera talk," he smiled. "Just, like, everything in the world is blocked out for that one moment. I'm just literally living in the moment. Proud and present."

'Strike missions'

Kemper was riding a wave of momentum through 2019 and early 2020 when he decided to make his fateful trip to Morocco. It was a trip that ended as it had begun, in a hurry. But the mood on the way out was very different to his palpable excitement and anticipation on arrival.

"It was at the end of my season last year and the Northern Pacific just started to fall apart," Kemper said. "There just wasn't the swells I was looking to see."

For some time, he'd been drawn to the idea of surfing the coast off Morocco in North Africa and it seemed as though the stars were aligning.

"One evening I was looking at all the swells across the world and I see this absurd storm moving through the Atlantic Ocean," he said.

He immediately contacted his buddies and the World Surf League to see if they'd be interested in tackling the waves and documenting it on film.

"This one just looked monumental," he enthused, "It looked a lot bigger and stronger than most swells that you see in that ocean."

Surfers refer to such adventures as "strike missions," they're planned at the last minute and the flights are booked with just 24 hours to spare, ensuring that the surf really is going to be worth the effort.

"If the forecast isn't well and conditions aren't good then we won't pull the trigger," Kemper noted.

In February, the strike team of Kemper, surfers Koa Smith, Luke Davis and filmmaker Arénui Frapwell arrived in Morocco, where they met up with Billy's friend, the local surfer Gerome Sahyoun.

He knew immediately that the hype was justified

"We surfed a handful of waves up and down the coast and there were probably some of the best waves I've ever witnessed in my life. It was truly the trip of a lifetime until the absolute worst happened."

Broken pelvis

Kemper says he has known death but isn't scared of it. At the age of just eight, he was mourning his brother and his mother died more recently of cancer.

What he does fear, though, is the thought of not seeing his own four children again. As a surfer, he doesn't fear the water, but he certainly respects it. "I'm by no means a master of the ocean, I always bow to the ocean."

As his broken body lay floating in the frothing waters off the coast of North Africa, the reality of his new situation rapidly came into focus.

"I knew what I had gotten myself into, I just didn't know how truly serious it was," he said. "Anyone who's ever broken their pelvis in half can relate to this. You're definitely not just going to walk up the beach."

Kemper says he owes his life to the friends who immediately rushed to his aid in the water and got him to safety. He was transported to the harbor on a jet ski, where an ambulance was waiting.

Of all the gory details he can recall more than a year after the dramatic event, it seems that this is still one of the rawest: "Even the ambulance ride felt like the worst pain ever. Every speed bump, every bump, the center of your body just opening up and releasing blood."

"Most people lose half their blood count," he said, speaking of his pelvis break. "You're going to need transfusions." He gestures with his hands to demonstrate his internal wound geysering blood at every bump in the road. "It's a pain you can't describe."

'Without surfing, I am not Billy'

After a few days in hospital, Kemper and his team realized they were facing more problems. Firstly, how to navigate a journey of more than 13,000 kilometers back to the US for emergency trauma surgery.

"I was in a state where I couldn't fly on a commercial plane, I couldn't fly business class," Kemper said. "With a pelvic break that bad, you can't leave a stretcher. Any bit of movement, you're just opening up that break to create more internal bleeding."

More pressing, however, was the looming Covid-19 crisis, which meant that international borders were being slammed shut all along their escape route home.

Having leaned on his community of family, friends and sponsors to help raise the funds for an emergency medevac flight, they were now in a race against time.

"It was literally just happening on the minute," he recalled. "It wasn't even like tomorrow, or this day, it was like 'Oh no! They shut down. They shut down. They shut down!' We're trying to beat them to the punch just to get an entry onto US soil."

Not only was Kemper desperate to see his family, but he also knew that the best medical care was at home, and it was treatment that was essential if he was ever going to compete on a surfboard again.

When they finally did make it back, Kemper was immediately rushed into trauma surgery by a doctor who'd been specifically researched by his team.

But even then, the road to recovery was a long one; months of grueling rehabilitation and the longest period of his life spent on dry land.

"I'd be pretty surprised if there was an athlete that outdid what I did in the five, six months I was up in California," Kemper said.

He moved in with his uncle, Hamilton and his wife Gabrielle Reece, and focused intensely on recovery, physical therapy and training. He details 11-hour days, seven days a week and reflects that the experience was probably a "blessing in disguise."

"What I learned last summer was probably more knowledge than I ever would have [acquired] without going through this injury," he said.

"It was beyond anything I thought I'd ever go through and I needed a few months to mentally prepare myself and heal my mind."

When the time came to climb back onto a surfboard again, Kemper says it felt like a rebirth.

"It was like the first wave of my entire life over again, it brought back the emotions of being a kid. This is why I've sacrificed so much; this is why I've worked harder than anyone, this is the reason why I belong here," he said.

"Surfing is who I am. Without surfing, I am not Billy."