I caught something out of the corner of my eye, a black shadow in the water. I thought it was a seal or a dolphin and then this fin broke the water."
Achmat Hassiem and his younger brother, Tariq, gathered their swimming gear quickly, anxious not to disturb their parents' weekend lie-in. On a quiet Sunday morning it did not take long to clear their Cape Town suburb and reach Muizenberg beach, the long stretch of sand that sprawls east of the Cape Peninsula. They were excited; life-saving exams were looming and a day of rehearsal lay ahead. It was 13 August 2006 and their lives were about to change for ever.
Down on the beach they met the others, Nick, Kim and Kiesha, and squabbled good-naturedly over who would be the patients and who the savers; and then who would be dropped where in the water. Hassiem, his memory five years later as clear as the Atlantic waters of False Bay, knew Muizenberg beach well as he had spent his childhood exploring it. "I stood in the water and watched the boat go back to the shore. The whistle went and the exercise began. I watched them pick up Nick."
Shark sightings around the Cape are common; so when Hassiem first caught sight of the advancing shadow, his initial thought was not one of alarm. Then the tell-tale fin first pierced the surface. "The shark was heading towards my brother. I screamed for the rubber duck [the life-saving boat] to get out to him. They didn't understand. Then I started splashing, trying to distract the shark. The shadow changed direction. It was coming towards me and then the fin disappeared. I knew when sharks attack they like to come from the bottom up. I could just touch the bottom and I tried to make myself big. But the shark didn't attack. It bumped me. I lost sight of the shark but I could see my brother. He was screaming. Then I saw it coming. Its mouth open.
"All I thought was to try and get away from its mouth. My hand was on the shark's head and I tried to get my right leg over it. I couldn't move my leg and then I saw half of it was in the shark's mouth. It started violently shaking me. I could feel my leg being torn apart but there was no pain. I was in absolute shock. I was being attacked by a Great White.
"The shark shook me again, as it headed towards deeper water and started picking up pace. I thought this was over, I was going to die. I was getting dragged deeper. The ocean was becoming darker. I remember thinking why don't I just let myself drown. Then I decided, no, fight. I had one good leg left and I was trying to kick it. Then it shook me again and so hard there was this cracking sound, even under the water – my leg broke off.
"I swam towards the surface and stuck my hand out of the water and that's when I saw my brother in the rubber duck. He grabbed me. I was hauled into the boat as the shark came back. It dwarfed the boat.
Later that day, Hassiem was operated on, and until the moment the anaesthetic took hold, he still had no idea what he had been through. Reality arrived the next day when he looked under the sheets and saw his leg was gone.
Sport had been his life before the attack and it was to be sport that was to help bring him back to life. "One day Natalie du Toit [an iconic South African Olympian and Paralympian swimmer] came to visit. She suggested I got into paralympic swimming. I didn't know anything about disabled sport – it's only once you are disabled you realise how big it is."
South Africa is one of the event's leading nations. They finished sixth in Beijing. Hassiem was part of that team, just two years after he lay in intensive care in Cape Town. "The first time I got back in the water was really difficult," Hassiem recalls. "The fear kicked in. It took a few weeks to get brave enough to do it properly."
He specialised in butterfly and freestyle and is now in the world's top 10. A medal in London is his next aim.
"There are still nights where I thank God I survived the attack and have had all these experiences," says Hassiem. "People say sorry, but the rewards that have come are amazing."
Follow Achmat Hassiem on Twitter – @achmathassiem