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(CNN) -- He grew up in a surfing party town on the U.S. "space coast" and has conquered waves in some of the world's most exotic locales, but these days Kelly Slater comes across more like an eco-warrior than a stereotypical beach dude.
The most successful board rider in the history of the professional circuit, he has seen up close the impact the human race has had on the planet's oceans during his illustrious career.
"This world is a scary place right now for the future of our children and their children and the next few generations," the 42-year-old tells CNN's Human to Hero series.
"Business is getting in the way of environmentalism and health, and at some point that's going to have to change.
"People really all have to figure out what's the most important thing, and that's water and food and air and, you know, the health of this planet."
The American points to the world's ever-increasing population as a major factor -- a seemingly inexorable growth that fuels the market for processed foods, with subsequent consequences for the health of those who consume them and the fragile eco-systems where the waste packaging often ends up.
The WWF reports that 80% of marine pollution comes from land-based activities, most of which has been produced in the past 60 years.
"People are unhealthy, diets are terrible and the pollution is awful -- tonnes of that stuff ends up in the ocean," adds Slater, who is on the advisory board for the Sea Shepherd Conservation Society.
"You have problems like not only oil spills and that kind of stuff but also the constant outpouring of plastics. Single-use plastics all through the ocean, degrading, turning into little bits that are all eaten by the sea life, and they're dying because their stomachs are full of stuff."
While nuclear power is seen by some as the answer to the planet's reliance on fossil fuels, the 2011 reactor meltdown in Japan has revived the safety fears that have dogged the industry since the Three Mile Island incident in Pennsylvania in 1979.
"You have Fukushima that's just polluting the air and water horribly with radiation," Slater says. "Even though it was caused by a tsunami, that's man-made technology that's causing that. It's frightening."
A 1970s child, Slater grew up in Florida's Cocoa Beach, immersed in hopes of a bright new future, with the Space Shuttle program well under way in nearby Cape Canaveral.
"I grew up watching all the shuttles launch and all the satellites and all the space missions -- obviously from way before I was born," he recalls. "My mom actually worked at the space center when she first moved to Florida.
"Cocoa Beach was very popular in the '60s and '70s. It was almost like a permanent spring break in our town. It was a funny mesh of people and it happened to produce a lot of really good surfers, even though we have very small waves."
Slater's father was a keen surfer, and also owned a local fishing shop, but his parents split when he was 11 and he would not reconcile with his dad until much later.
Meanwhile, Kelly's relationship with his older brother would be a precursor to his hyper-competitive surfing career.
"I had a certain family dynamic where I think I felt from a young age that I needed to prove myself to people and to become successful at something, to feel like I was important," he says.
Young Kelly "was pretty good at baseball, I liked to play basketball a little bit but I was kind of small."
"I was pretty tough and fast so I was pretty good at football, but I just didn't love it," he says.
"When I was in kindergarten or first grade, I started to think, 'Gosh, I think I'm a surfer.' I remember thinking, 'That's what I am if you were going to call me something. I like to surf more than anything.' "
Slater won the first of his record 11 ASP World Tour titles in 1992 when he was 20. He is still the youngest to be champion, and the oldest -- having won his most recent crown in 2011, aged 39.
He has had his own video game, played guitar on stage with rock band Pearl Jam, released his own album, and made several surfing films.
But it was his appearances in the 1990s hit TV show "Baywatch" that helped propel him to mainstream popularity.
Not that he enjoyed the experience at the time.
"Baywatch was somewhere between funny and painful! I really didn't want to do the show," says Slater, who quit after featuring in just seven episodes spread over two seasons.
"I felt like I did horribly on the casting ... it was almost like I was going there for my interview to go in the draft for war. I was like, 'I'll screw this up for sure,' and somehow they liked me."
He says it put him firmly under "a microscope in our small community" -- a situation that was amplified when he started dating one of the show's stars, Pamela Anderson.
"I was 20 years old. I got engaged that year, I won the world title, then the next year, I had a horrible year -- I lost the world title, my engagement broke up. I quit Baywatch that same year," he says.
"I was also broke. I lost all my money so I was in debt and I had 'I Owe Yous' everywhere to people. I had a real tough learning curve from the time I was about 20-22.
"But I look back on it now and I laugh. I enjoyed it, in all honesty. I still have friends from the show. Anything in the world has good people involved in it and I met some really great people there."
Slater bounced back to win five consecutive world titles from 1994-98, but shocked the surfing world by then going into semi-retirement, having become burnt out and "totally bored with life."
"I was a competitive machine, and my friends hated me. I'd win 25 grand in a contest and wouldn't buy anyone dinner," Slater said in 2006.
He was reunited with his father during his surfing hiatus, but Steve Slater -- who had battled problems with alcohol -- died of throat cancer in 2002 not long after Kelly had decided to return to the tour.
However, with a newfound perspective in life, Slater reestablished himself as a champion, winning titles in 2005-06, 2008 and 2010 and surpassing one of his childhood heroes, Tom Curren, in all-time career wins.
He has also worked hard to break the stereotype of the "surfer dude." Slater's close-shaven dome is not all that separates him from the bleached-blond stoner clichés.
"I've always lived a clean life. As I've gotten older, that's become a lot more about my diet too," he says.
"When I was a kid, I ate a lot of sugar and bad food and didn't worry about that, but as I got older I realized that it can give me an edge and make me feel better, and I can have more longevity. That became a big part of my mantra too."
Slater has found himself less comfortable with the attention his celebrity brings -- something he had craved growing up, when he dreamed of being an actor like comedian Steve Martin.
"As a young kid I was very outgoing. I'd get in fights at school, and I had no reservations about just being anything. But as I got older and I started to realize people were looking at me, I became a bit more shy. And I think it changed my personality quite a bit," he told CNN last year.
Talking to CNN again last week, he added: "It's so nice to have people you know smile when they see you and get all happy, and kids that run up to you. It's something that maybe not many people will ever experience ... and at the same time, I think the more I have it or the longer I have that as part of my life, the more I feel like I want to shy away from that.
"Sometimes I get really shy -- I have this certain sort of shyness inside me where I just want to disappear sometimes."
One thing that Slater is keeping private, for now, is his long-term project to build an artificial wave facility.
"We've have been working on this technology to create the perfect wave. It's a private one, in a sort of secret location in California and it should be done sometime in the first quarter next year," he says.
His love of golf, however, is very public. A regular competitor on the celebrity pro-am circuit, Slater admits the sport is a "giant fetish."
"There's a certain Zen to golf because it's about accepting your mistakes. I personally think anything in life is philosophical and spiritual if you use it the right way, but golf is a challenging thing that's hard to accept the result of," he says.
"A lot of times you want to break a club or scream or cuss or whatever, but when you get beyond that you just accept it and you learn something real quick.
"Really good golf is a combination of all those difficult, terrible thoughts and then something super easy, and you're like, 'Oh that's it.' And you have that feeling without even thinking about it."
That philosophical mindset has helped Slater extend his career, and he says surfing will be a "lifelong journey."
"I want to keep learning and keep adding layers to what I do, and keep getting better. I feel like the better I surf, the more fun it is," he concludes.
"If you're better you can do the things you envision, and go out and actually physically recreate them. And that's success, I think."
Maybe, if enough of us thought that way, the future wouldn't be so frightening after all.