CAPE TOWN, South Africa -- After yelling to his brother that a great white shark was swimming his way, Achmat Hassiem watched as it changed course - toward him.
The 13-foot shark bit his foot, shook violently and took him under. Seconds later, Hassiem was pulled into a nearby boat, alive but missing his right foot.
The August episode in False Bay was the most recent in a string of great white incidents around Cape Town that have stirred emotions about a creature often demonized, intensifying a debate over how to balance safety and conservation.
Some surfers say "rogue" sharks that repeatedly turn up near people should be killed. Researchers say there are no rogue sharks and that a hunting ban imposed by South Africa in 1991 is crucial to the endangered species' long-term survival.
In an attempt to explain the attacks, some have pointed to the growing cage-diving industry that puts tourists in an underwater cage and lures great whites for a close encounter. So far, no research has shown such a link. Others suggest that overfishing has lured hungry sharks closer to shore. And some say there are simply more people in the water.
Seemingly all agree that there has been an increase in unprovoked shark bites on people, or small boats, along Cape Town's nearly 200 miles of shoreline. In the past four years, 13 have been recorded, with three fatalities; in the previous 42 years, there were 17, one fatal. Nearly all are thought to have involved great whites. In two of the recent fatalities - a woman swimming and a spear fisherman - the bodies were never recovered.
"We're looking for a balanced approach to this issue without flying off the handle and reacting every time something happens," said Gregg Oelofse, Cape Town's environmental policy and research coordinator.
To that end, the city is expanding to 11 beaches a shark-spotting program that a group of surfers started at two beaches in 2004. Lookouts on hillsides or in towers sound a siren to warn of a shark and can close a beach until the fish swims away. The city plans to put independent observers on cage-diving vessels in False Bay to ensure that operators do not feed sharks, which could condition them to associate boats with food, and do not abuse the animals by enticing them to smack the cage to heighten the thrill for tourists.
Cape Town is also exploring the viability of using exclusion nets to keep sharks from beaches. Unlike shark nets used off Durban on the Indian Ocean, exclusion nets have fine mesh that does not entangle sharks or other creatures. The nets could be removed whenever whales are near.
But apart from the shark-spotting, none of the measures would enhance safety for surfers, kayakers and surf skiers who venture hundreds of yards from shore. Nets, for instance, would work only in calmer water between breakers and the shore.
The relative newness of kayaking and surf-skiing in Cape Town, along with advanced wetsuits that enable surfers to stay in the chilly water for hours, have raised the odds of shark encounters, Oelofse said. Most here involve great whites, considered the predator of the seas, and can occur when a shark mistakes a person for a seal or is simply curious or aggressive.
In July, Lyle Maasdorp, 19, had a close call off Fish Hoek while riding a surf-ski.
"Lyle said he felt the back of his surf-ski lifting out of the water and he heard a crunching sound," the National Sea Rescue Institute wrote. "He fell off his surf-ski and realized it was a shark when his hand landed on the shark's back."
Unhurt, Maasdorp scrambled onto another person's surf-ski and found safety on some rocks.
Paul Botha, who has surfed these waters for 40 years, said he fears surfing alone now.
"The instant I'm alone, 'shark' comes into my head. That thought comes jolting up my spine. I'm looking around, wondering what's going on beneath me," he said.
Botha, an event promoter, has riled shark researchers by calling for "selective culling" of rogue sharks. He questions how they know rogue sharks are a myth when so much about great whites - their mating, breeding, migration patterns, population - is so poorly understood.
He also calls for sonar buoys to track sharks, a system he likens to the use of closed-circuit cameras to deter crime. The technology exists, but some experts say it might not be practical yet. An existing option for surfers is to wear electronic "shark shields" that emit weak pulses shown to repel sharks.
Botha blames the rise in attacks on overfishing that has deprived sharks of food, protections enacted in 1991 that he believes have increased the shark population, and cage diving.
Most of his views are not shared by researchers such as Alison Kock, a doctoral student at the University of Cape Town. She says an increase in people using the water, not more sharks, explains the rise in attacks, which is part of a global pattern. Because it takes sharks a decade to mature sexually, she said, it is "physiologically impossible" that the 1991 protections have caused a population boom.
She dismisses the theory of a rogue shark by pointing out that hundreds of great whites have been identified and thousands of people enjoy Cape Town's waters, yet attacks are still relatively rare.
"If these sharks were man-eaters, there would be an attack every day," she said. And because great white sharks are migratory animals, killing five or 10 would make little immediate difference because five or 10 more would soon swim into these waters.
Kock co-authored a study that found no evidence that cage diving raised the risk of shark attacks. Chumming, in which a trail of blood and fish meat is spread behind the boat, did not hold sharks' interest for long. And sharks rarely ate the fish heads used as bait.
"Conditioning can only arise if white sharks gain significant and predictable food rewards," the authors wrote. Even if such conditioning occurred, it is "highly improbable" it would endanger people, because the boat, cage and tourists - as a unit - do not resemble surfers or swimmers.
Yet, Kock expressed criticism of some cage-diving operators that play up the fear factor and reinforce myths.
"The industry needs to take the lead and say, 'We're not selling this as an adrenaline sport; we want to be educational.'"
Of the 12 cage-diving operators, eight are in Gansbaai, southeast of False Bay. Marine biologist Michael Scholl works as a guide on the cage-diving boat Shark Fever, a job that enables him to do research on great whites.
Scholl has developed a visual identification system that uses dorsal fin markings. He has identified 1,200 great whites since 1998 in and around Dyer Island, which is populated by seals. While South Africa's Western Cape coast is clearly a prime shark habitat, he said population estimates remain elusive.
One recent morning, Shark Fever took out 15 tourists. The cage can hold four or five people and is lashed to the boat's side, with the top above water. Tourists wear wetsuits and masks, and hold their breath as they watch the sharks swim.
In three hours, Scholl and his research assistants spotted 10 great whites, some 10 to 12 feet long, less than a mile offshore. Three or four times a shark got the bait before it could be pulled from the water. In some instances, a shark lunged out of the water, exposing its teeth, or rattled the cage while thrashing for the bait.
The cage-diving operation that employs him has a brochure with "Jaws" printed on it. But Scholl says he is trying to change that image through an hourlong seminar he gives before every trip. He says responsible cage diving not only aids research but can demystify great whites.
"The more people see those white sharks out there for what they are, the less people will be afraid of sharks," he said. "That's why I'm supporting it. I think it's a great tool for education."
As for shark-related deaths, which number a handful per year worldwide, he said: "It's such a small number. More people have died today in this country from AIDS, many more. Yet sharks make the news."