Paralympic swimmer Achmat Hassiem uses special motivation to go fast: He imagines being chased by the great white shark that bit off his right leg.

The South African was attacked by a shark off the coast of Cape Town six years ago after he lured the great white away from his younger brother. Before then Hassiem had competed in various sports, including swimming, but wasn't sure what to do after losing his leg.

It was South African Paralympic swimming champion Natalie du Toit who encouraged Hassiem to get back into the water. Before long, he started breaking his country's Paralympic records.

"I took to the pool like a shark in the ocean," he said with a laugh.

The 30-year-old Hassiem came to the London Paralympics determined to do better than his ninth-place finish at the Beijing Paralympics four years ago. On Saturday, he won bronze in the men's 100-meter butterfly.

"My little secret is obviously that I just try and imagine I'm in the ocean and I've got a 4 ½-meter great white shark at my feet," Hassiem said. "It's definitely good motivation to swim fast."

In 2006, Hassiem was the first to spot the shark when he and his brother Taariq were on a lifeguard exercise off a popular beach in Cape Town. He shouted to colleagues in a nearby boat to get Taariq out of the water, while Hassiem distracted the shark by slapping the water.

The shark then bit Hassiem's right leg and dragged him about 50 meters.

"I gave one last enormous push and heard a great snapping sound," Hassiem said of the moment he lost his leg.

As he was being pulled onto the boat by his brother, Hassiem said he looked back and saw the shark chewing on what must have been his foot.

"I believe I lost my leg for a good reason," he said. "Losing a leg is nothing compared to losing my brother, so I'm just trying to make the best of it."

Du Toit, one of the most decorated Paralympians who was also the first amputee to compete against able-bodied swimmers at the Olympics in 2008, said Hassiem was an inspiration to others.

"It's been great to see Achmat do better and better in the last couple of years," she said. "I think he's become a role model because people look at him and wonder how they would cope in that situation. He's just gotten on with it and kept going."

Later this week, Hassiem will swim in the 100-meter and 400-meter freestyle events.

"That shark turned my life around for a reason," he said, "and I've got to make the best of all my opportunities now."