The 52-year-old American, an 11-time world champion, had already been ruled out of the Paris Olympics this summer. "This feels like the end," he said, fighting back tears, after being knocked out of a World Surf League event in Margaret River, near Perth. He did not say definitively that he was retiring, having asked for a wildcard for an upcoming event in Fiji.

He was visibly emotional as he was carried off the beach in a show of respect and applauded by fans and fellow competitors. "Everything comes to an end. If you don't adapt, you don't survive. My motivation just wasn't there to really give the 100 per cent that everyone is giving now," said Slater, who has been compared to basketball's Michael Jordan in how his fame transcended his sport.

Australian three-time world champion Mick Fanning, who retired from the sport in 2018, congratulated Slater on an incredible career: "What you've done for the sport of surfing is unparalleled. You have pushed the boundaries of what is possible. Your dedication to your craft has inspired everyone to be better. Thank you for all the memories and battles," he wrote on Instagram.

Renowned for his skill and style, the ultra-competitive Slater burst onto the surfing scene in 1990, winning his first world title two years later at the age of 20 and his last in 2011 to become both the youngest and oldest world champion.

Slater has also appeared in video games and dozens of surfing movies. He also starred in the hit 1990s TV show 'Baywatch'. "It's been an incredible life full of memories," said Slater, who has a baby on the way with partner Kalani Miller. "Now is the start of something else, the start of the rest of my life. It's not all roses, but these have been the best times of my life," he concluded.