In the murky predawn light, our speedboat hurdles across Cape Town, South Africa's False Bay. A fierce wind whips the seas, pitching our 26-foot craft and sending an eerie scream across the white-tipped waves. We are hoping to come face to face with one of the earth's most feared predators: the great white shark. Alison Kock, a marine biologist, has made this journey more than 500 times since 1999, striving to unlock the shark's many mysteries.

We approach a flat, rocky island a quarter-mile long and crowded with about 60,000 Cape fur seals. "They want to go to sea to feed, but they're afraid of the white sharks," Kock says. The hungry seals dive into the water in a desperate swim for their feeding grounds 40 miles out in the bay. They must run a gantlet of great whites waiting for them just off Seal Island.

The attacks begin a few minutes later. A 3,000-pound great white explodes out of the water. In midair the shark lunges at a seal and flips back into the water with a mighty splash. Moments later another shark breaches and bites a seal. We speed to the spot, in time to see a pool of blood. Scores of gulls hover above, screeching in excitement, then swoop down to gobble up any leftovers.

During an hour and a half, we witness ten great white sharks hurtling out of the water to grab seals. As the rising sun brightens the sky, the attacks stop.

"That's it for today," Kock says. "The great whites only attack in the hour after dawn. We think it's because once there's enough sunlight, the seal can see the shark coming at it from below and escape."

Despite this awesome display of predator power, Kock and other researchers claim that the shark has been defamed: its reputation as a ruthless, mindless man-eater is undeserved. In the past decade, Kock and other shark experts have come to realize that sharks rarely hunt humans—and that the beasts are sociable and curious. Unlike most fish," Kock says, "white sharks are intelligent, highly inquisitive creatures."

Perhaps the largest great white shark ever caught was off Malta, in the Mediterranean Sea, in 1987. It was reported to be 23 feet long and weigh 5,000 pounds. (Many scientists are skeptical and put the maximum length for a great white at closer to 21 feet.) A sea turtle, a blue shark and a dolphin, and a bag full of garbage were found in the giant's innards.

The great white shark is a top predator throughout the world's temperate and subtropical waters. It's found most commonly off South Africa, New Zealand, Australia and the United States, where most sightings occur in the waters off California and the mid-Atlantic coast. With its torpedo shape and heavily muscled tail, a great white can swim 15 miles per hour or faster when attacking. It has about 240 serrated teeth in up to five rows.

No one has seen great white sharks mate. Males are distinguished by a pair of sperm-delivery organs called claspers that extend from the pelvic fins. After mating, eggs hatch inside the female's uterus. Gestation takes at least a year, then 2 to 12 babies are born. In some shark species, the strongest fetuses eat their weaker brothers and sisters in the womb; no one knows whether great whites do so.

Sailors have feared great white sharks for centuries. In 1862, Jonathan Couch wrote in his History of the Fishes of the British Isles that in the West Indies, the great white "is the dread of sailors who are in constant fear of becoming its prey when they bathe or fall into the sea." In 1812 the British zoologist Thomas Pennant wrote that "in the belly of one was found a human corpse entire, which is far from incredible considering their vast greediness after human flesh."

But the great white shark entered the landlubbers' pantheon of most terrifying creatures only in 1971, when a great white approached a dive cage in a documentary called Blue Water, White Death. The film inspired American novelist Peter Benchley to write the book Jaws, about a great white terrorizing a New Jersey seaside community. Heart-thumping fear spread around the world in 1975 when a then little-known director, Steven Spielberg, directed a movie based on the novel. Jaws was the first film to earn $100 million at the box office, and it launched the era of the summer blockbuster.

Leonard Compagno, one of the foremost experts on sharks, helped design the mechanical great white used in the movie. "When they made it a huge male with its characteristic claspers, I told them they'd got it wrong because the biggest great whites were females. The art director told Spielberg, who brushed aside my objection. He wanted it to be an enormous male great white, and that was that." Compagno knew the movie was a "monster gig," but he did not anticipate how seriously people would take it. "The movie great white scared the hell out of people, and made the shark much feared," he says. In reality, great whites "rarely bother people, and even more rarely attack them."

Compagno, 64, has run the Shark Research Centre of the Iziko South African Museum for more than two decades. He became fascinated with the animals as a child growing up near Monterey Bay, California, and studied them as a graduate student at Stanford. He took a job in South Africa in 1984, during the apartheid era, and "got a bit of flack from a few scientific colleagues," he says. But South Africa is one of the best places to study great whites.

Much of his work entails observing behavior, and he's found the fish to be a surprisingly intelligent creature. "When I'm on the boat, they'll pop their heads out of the water and look me directly in the eye," he told me. "Once, when there were several people on the boat, the great white looked each person in the eye, one by one, checking us out. They feed on large-brained social animals such as seals and dolphins, and to do this you have to operate on a level higher than a simple machine mentality of an ordinary fish."

Compagno has also found that they are not lone hunters but social animals. When great whites gather, he says, "some are assertive, others relatively timid. They body-slam, gape or carefully bite each other in dominance displays." Fishermen have told him they've seen the sharks hunt cooperatively. "One great white will draw the attention of a seal, allowing another to come from behind and ambush it," Compagno says.

And he swears that the sharks display curiosity. Seals, penguins and other animals sometimes have scars from shark bites; Compagno says the bites were investigative, not predatory. One of his students has watched a shark catch a seal in its mouth and toss it into the air repeatedly. Alison Kock says she saw a great white sneak up below a bird floating on the water, "gently" grab the bird in its mouth and swim around the boat. A few seconds later the bird resurfaced and flew off, hardly the worse for wear. Compagno even says that "some 'shark attacks' on humans by white sharks seem playful; I interviewed two divers here who were grabbed lightly by the hand by a white shark, towed a short distance and then released with minimal injury."

The great white shark attacks near Seal Island end as suddenly as they begin. The sea gulls stop screeching. Kock drops anchor and chums the water with a slurry of pulped sardines and tuna. "Great whites can smell this from a mile away and come because they think there's been a kill." She baits a hook with a large tuna head and throws it into the water.

"Shark!" she shouts, and I see an enormous dark fin slice through the water near the boat. I should know better, but I can't help it: on the tip of my tongue is the Jaws theme music, the heart-pumping duh-dum, duh-dum, duh-dum. Kock says that it's a female, about 11 feet long. Swimming with graceful power, the shark follows the tuna head as Kock's assistant pulls it to the boat before the shark can get a bite. Kock balances against the side wielding a modified spear gun with a blue electronic tag at the end. The shark pulls away untouched. It skirts the boat, swims to the other side, turns and—I swear—looks me straight in the eye.

The shark returns an hour later, and Kock is finally able to inject the tag on its right side, below the dorsal fin. The great white body-slams the boat, shaking it, then swims away.

Kock has tagged 75 great white sharks with electronic markers since 2003. She had divers set 35 detectors in the seabed around False Bay. Whenever a tagged shark passes within about 1,600 feet of the instruments, they record the time, date and identity of the shark. It's mid-September, almost summer in the Southern Hemisphere, and her research has shown that the great whites will soon abandon Seal Island and move closer to shore, patrolling the water just beyond the breakers.

Another great white approaches the boat but doesn't come close enough to be tagged, and Kock decides to check the inshore waters. We approach a beach where dozens of people are swimming. Kock spots a huge silhouette below the surface and steers the boat closer. "She's almost 15 feet long and weighs more than 4,000 pounds," Kock cries with excitement. It's the second-largest great white shark she has seen this year.

I stare, barely able to absorb the animal's immensity. Kock follows the shark, but it pulls away. After trying for an hour to tag the beast, Kock gives up. It's the one that got away.

Despite scientists' years of research on great white shark biology (see sidebar), they still have lots to learn about behavior—and migratory patterns. In 2003, Wildlife Conservation Society researchers attached an electronic tag to a shark named Nicole off the coast of South Africa. The tag was programmed to record the shark's position for 99 days before detaching. When the tag surfaced off the coast of Western Australia—roughly 6,800 miles away—it was the first record of a great white shark migrating between oceans. Nicole was apparently on a round-trip journey, because in August 2004, researchers spotted her distinctive dorsal fin back in South African waters.

A recent study of California's great white sharks found similar patterns. Some sharks make annual journeys to the Hawaiian Islands and back to the same beaches where they were tagged. Oddly, though, even more of them swim to a spot about halfway to Hawaii, a shark hot spot previously unknown to researchers. Stanford marine biologist Salvador Jorgensen calls it "the white shark café." He isn't sure whether sharks gather there to eat, to mate or for some other reason entirely.

Another surprise to come out of recent tagging studies is that great whites from California and Hawaii do not mingle with those from South Africa and Australia. No one knows why. This could pose a problem for conservation efforts: if one population shrinks, it cannot be replenished from the other side of the ocean.

Great white sharks' numbers have plummeted; along the U.S. Atlantic coast, for instance, the population has declined by more than 75 percent in the past two decades. The main culprits are commercial net and long-line fishing, which inadvertently snare sharks; fin hunters, who sell their hauls for shark fin soup; and the illegal international trade in great white jaws and teeth. "I've seen the bodies of great whites with their jaws cut out," says Mike Rutzen, who runs a shark-diving business in South Africa. "A jaw with all its teeth can fetch $25,000 on the black market in the U.S., and a single tooth can cost $500." Shark fin sells for $300 or more per pound. Hunters usually cut off the dorsal and pectoral fins and toss the body back in the water. Unable to swim, the shark can't pass oxygen-rich water through its gills and drowns.

South Africa was the first country to ban commercial hunting of great white sharks, in 1991, followed by Namibia, Australia, the United States, Malta and New Zealand. The great white was listed as "vulnerable" by the United Nations in 2000, and in 2004 the Convention on International Trade in Endangered Species (CITES) outlawed most international trade in its jaws, teeth, fins or meat. California and Florida have placed a total ban on killing the species, frustrating sports fishermen. Not that the great white should be regarded as much of a trophy. "The great white is one of the easiest of fishes to catch," says Rutzen. The sharks will follow bait right up to a boat.

Alison Kock says great white sharks are drawn toward land during the summer when other fish arrive with the warm currents. She shows me a photograph of a beach where I have gone swimming in Cape Town. A 16-foot female great white lies next to Kock's boat, disturbingly close to children playing in the shallows. The researchers never chum near swimmers, but find sharks with the help of spotters on coastal mountains who scan the waters with binoculars. (The spotters' primary job is to alert lifeguards when a shark is near.) "It's very rare for great whites to attack humans as prey," Kock says. "Imagine the hundreds of thousands of swimmers here each summer, and then count the number of attacks. Over the past few years you can count them on one hand."

Three years ago, about 20 yards from the Cape Town shoreline, Tyna Webb, 77, was taking her morning swim, as she had done for 17 years. "From the beach I saw the fin, then the whole shark coming out of the water," a witness to the attack later reported. All that was found was Webb's red bathing cap. A few years earlier, only three of four South African spear-fishermen who went underwater together resurfaced. Compagno examined the missing diver's wet suit when it was recovered. "The tear marks indicated it was a great white shark that had somehow cut him out of the suit and devoured him," Compagno says.

There have been 236 great white shark attacks on humans recorded since 1876. About one-third have taken place in California waters. This past April, triathlete David Martin was killed by a great white north of San Diego. One attack that particularly haunts me happened in Australia in 1993. Newlyweds John and Deborah Ford were scuba diving at a seal rock 400 miles north of Sydney. They were decompressing a few yards below the surface when John saw a 16-foot great white heading toward his wife. He pushed her out of the way, and the shark swallowed him.

Despite this grisly and disturbing history, Compagno says great whites intentionally attack humans even less frequently than the statistics suggest. Compagno says many "incidents" (a term he prefers to "attacks") are "bite and release." He thinks the shark is trying to get a better look at the strange creature in the water. According to the International Shark Attack File, a record kept by marine biologist George Burgess at the Florida Museum of Natural History, great whites leave the area two-thirds of the time after the first bite. According to his records, over 80 percent of people supposedly attacked by great whites in the 1990s survived. "If the great whites really attacked the people listed on the file, hardly any would have survived," says Compagno.

One encounter that was widely referred to as an attack—but almost certainly wasn't—took place this past October in Australia. A tourist on a kayak claimed she'd beaten an attacking great white shark off with a paddle. She required four stitches. "If the great white attacked her, she'd be mincemeat," says Compagno. The wound was probably caused by the sharp scales on the shark's skin brushing against the woman's arm.

The hamlet of Gansbaai, 100 miles southeast of Cape Town, bills itself as the great white shark capital of the world. Mike Rutzen's family—including his mother, sister, brothers, niece and nephews—opened a cage-diving business here in 2001. Brad Pitt has taken the plunge with the Rutzens three times; Leonardo DiCaprio and Britain's Prince Harry have also taken to the Rutzen cages.

But there are only excited tourists, Rutzen, the crew and me aboard the Barracuda today. Rutzen is famous around Gansbaai for diving with great whites without a cage. "The first time I was really scared," he tells me as we head out through a mist, "I was right by the boat and she came close to me. I nervously prodded her away with a spear gun. She swam away a few yards, turned and surged back at me. She thrust her face at mine and opened wide her enormous mouth to show me her teeth, and swam away. She was saying, 'Don't do that again.'"

A film shot for an "Animal Planet" TV program shows Rutzen with eight curious-looking great whites circling him. He strokes the nose of one, prompting it to open its mouth wide just inches from his face. It is a reflex response, not a threat display. Then the sharks are apparently scared away by the arrival of a larger 15-foot female. The female swims around Rutzen a few times, seemingly checking him out. He grabs hold of her dorsal fin, and she tows him about 100 yards underwater.

I have no intention of joy riding on the back of a great white shark. But I do plan to offer myself at close range to see if the animals consider me prey. We drop anchor about a mile offshore from a popular beach. Six other dive boats idle nearby, and within 30 minutes every one of them has a curious great white hovering around it. Rutzen's nephew, Morné Hardenberg, throws out a tuna head attached to a rope while two crew members pour scoops of chum into the water. "Shark!" Rutzen cries as a huge triangular fin breaks the water about ten yards from the boat. The great white makes straight for the tuna, and Hardenberg draws the shark up to the boat before pulling the bait on board.

Feeding wild sharks is illegal in the United States, and conservationists are pushing to ban the practice in South Africa. "Sharks are trainable animals," says Florida marine biologist Burgess. "They learn to associate the humans and the sound of boat engines with food, just like Pavlov's dog and the bell. So what we really have then is an underwater circus." An Austrian tourist diving—without a cage—in chummed waters in the Bahamas was bitten on the leg by a bull shark this past February. He died of blood loss the next day, the first death Burgess says can be attributed to shark feeding.

Rutzen says that his crew members never actually feed sharks: they always pull their tuna-head bait into the boat before a shark can get it, and he says the small bits of flesh in the chum fall to the seafloor. But there's no question that the prospect of food whets a shark's appetite.

I scramble into the dive cage with three other shark watchers. We duck our heads underwater to watch the shark as it chases the bait. As it swims by us, its snout bumps against the cage. I stand up on a bar across the middle of the cage, my body halfway out of the water. Rutzen yells "Shark!" and a great white breaks the surface with its snout and looks directly at me. For a few moments I feel real terror. Hardenberg flings the bait again, and the shark follows it to the boat, coming so close that I can reach down and touch its rough skin. The shark doesn't notice; it's focused on the tuna. Three more great whites arrive, attracted by the chum. They follow the bait, ignoring the bigger and tastier meal—me—just inches from their giant jaws.

One shark bucks the system. For the fifth time it follows the tuna head toward the boat. When Hardenberg yanks the tuna aboard, the shark body-slams the small cage, almost knocking me off my perch. As I cling to the bars, it swats at me with its enormous tail, barely missing my head.

I don't think the shark wanted to eat me; the tuna head smelled and moved more like shark food than I did. I stay at the top of the cage as the great whites make ten more lunges at the boat. It's a thrill. It's terrifying. But it's somehow comforting that the sharks don't seem to think of me as prey.

Paul Raffaele was injured by a bomb blast in Afghanistan in April while on assignment for Smithsonian. He is expected to make a full recovery.