RIO DE JANEIRO -- Before Achmat Hassiem hops onto the Paralympic starting blocks in Rio, he'll close his eyes and think of Scarlet.

She's the 4.7-metre great white shark that took his leg but not his dreams, and launched him on an illustrious career path that earned him an award from the United Nations.

"It's my little way to get my adrenalin pumping. When I get behind the blocks, I imagine I'm in the ocean, and this massive great white is in the water, and she's saying 'Hey Achmat, I'm right behind you. I'm coming for you,"' the South African says of the great beast he named Scarlet -- more out of reverence than rage.

"Then I swim as hard as I can to get away from her. Hopefully I can get away from her at gold-medal pace."

The Paralympic bronze medallist will swim the 100-metre butterfly on Monday, and the 100 freestyle on Tuesday, nearly a decade to the day after his shark attack in False Bay, off the shores of Cape Town's Muizenberg Beach.

Sharks are regularly spotted in False Bay, and make for a remarkable sight when they breach the surface to attack seals.

Hassiem was a semi-professional soccer goalkeeper, and was participating in a lifeguard drill that morning with his younger brother Tariq. The two were treading water when Hassiem spotted the shark's telltale grey fin slicing through the water toward his brother.

Hassiem slapped the water's surface to distract it, and as Tariq was pulled to safety by the lifeguards in the rescue boat, the shark turned.

"The most incredible thing I remember is seeing the power of the tail. It was kicking its tail to turn around, using that force to drive itself forward toward me," Hassiem said.

The shark's massive jaws came down on his right leg, and she started to drag him under.

"The worst part was listening to the sound of the rescue boat disappearing in the background as I was pulled underneath the water. I thought to myself, 'With that sound goes all hope,"' Hassiem, now 34, said through his distinct South African accent.

"I thought I was going to drown, my lungs felt like they were going to explode. With my last breath, I decided to fight back, I started hitting the shark with my hands and kicking it with my free leg.

"Eventually the shark pulled away and that's when I heard snap-crackle-pop, and boom, my leg broke in half."

It wasn't until he awoke in intensive care that he learned of the severity of his injury.

"My brother was standing next to me and he was crying, and he said 'Thank you for saving my life.' I said, 'It doesn't matter. You're alive and I'm alive, and that's the most important thing.' He told me 'But you didn't come out that great. Look underneath the blanket."'

Hassiem, who had dreams of perhaps playing for one of the world's top soccer clubs one day, was devastated.

"I thought 'All my dreams disappeared with that leg,"' he said.

Far from it. South African swimmer Natalie Du Toit, one of the world's most decorated Paralympians, paid Hassiem a visit, and encouraged him to try swimming. Du Toit famously competed against able-bodied swimmers at the Beijing Olympics, and ended her career with 13 Paralympic gold medals.

Hassiem would finish ninth in his Paralympic debut in 2008, and then in 2012 in London, after racing to bronze, the crowd applauded his efforts with chants of "Shark boy, Shark boy!"

Hassiem wears the nickname proudly.

He's also become a fierce ally of the feared ocean creatures, an outspoken advocate for shark conservation. He's active in the Save Our Seas Foundation, which funds research to conserve marine life, and was named a Global Shark Guardian by the United Nations' Save our Sharks Coalition in a ceremony in New York.

"At the end of the day, the shark has given me so many opportunities in my career," Hassiem said. "I've represented my country at three Paralympic Games, I got to tour the world with great teammates, and motivated people around the world with my (public speaking)."

He talked of a responsibility to give back to Scarlet and her kind.

"Who better to speak for the shark than a shark attack survivor?" he said. "I see myself as an ambassador for sharks, a 100 million sharks are killed per year. They all play an integral in the food web, and if you take sharks out of the food web, the food web will fall apart, and the ocean will fall apart. We, as human beings, won't be able to survive in this world.

"So in turn, I kind of see it me helping save the world. Which is really, really cool."

Hassiem said he's seen images of Scarlet since the attack. The giant fish -- think of three average-sized men stacked one upon the other -- is recognizable by the large scar across her face.

"It's absolutely phenomenal to see the way she is, and just to see great white sharks in their natural habitat."