An ocean without its unnamed monsters would be like a completely dreamless sleep.
 
—John Steinbeck, THE LOG FROM THE SEA OF CORTEZ
 
The killing took place at dawn and as usual it was a decapitation, accomplished by a single vicious swipe. Blood geysered into the air, creating a vivid slick that stood out on the water like the work of a violent abstract painter. Five hundred yards away, outside of a lighthouse on the island’s highest peak, a man watched through a telescope. First he noticed the frenzy of gulls, bird gestalt that signaled trouble. And then he saw the blood. Grabbing his radio, he turned and began to run.
 
His transmission jolted awake the four other people on the island. “We’ve got an attack off Sugarloaf, big one it looks like. Lotta blood.” The house at the bottom of the hill echoed with the sounds of scientist Peter Pyle hurrying, running down the stairs, pulling on his knee-high rubber boots, slamming the old door behind him as he sprinted to the boat launch.
 
Peter and his colleague Scot Anderson, the voice on the radio, jumped into their seventeen-foot Boston Whaler. The boat rested on a bed of rubber tires beside a cliff; it was attached to a crane which lifted it up and into the air. The crane swung the whaler over the lip and lowered it thirty feet, into the massive early winter swells of the Pacific.
 
Peter unhooked the winch, an inch-thick cable of steel, as the whaler rose and fell into troughs big enough to swallow it. He started the engine and powered two hundred yards toward the birds, where the object of all the attention floated in a cloud of blood: a quarter-ton elephant seal that was missing its head. The odor was dense and oily, rancid Crisco mixed with seawater.
 
“Oh yeah,” Peter said. “That’s the smell of a shark attack.”
 
In a world where very little is known for certain, they knew that below them a great white shark was orbiting, waiting for the seal to bleed some more, and that this shark would soon be returning for breakfast. It might be Betty or Mama or the Cadillac, one of the huge females that patrolled the east side of the island. These big girls, all of them over seventeen feet long, were known as the Sisterhood. Or it might be a “smaller” male (thirteen or fourteen feet), like Spotty or T-Nose or the sneaky Cal Ripfin. These sharks were called the Rat Pack. It might be any number of great whites. At this time of the year there were scores of them cruising this 120-acre patch of sea, swimming close to the shoreline of Southeast Farallon Island as hapless seals washed out of finger gulleys at high tide and into the danger zone.
 
In any given year more than a thousand people will be maimed by toilet bowl cleaning products or killed by cattle. Fewer than a dozen will be attacked by a great white shark. In this neighborhood, however, those odds do not count. At the Farallon Islands, during the months of September through November, your chance of meeting a great white face-to-face is better than even money, should you be crazy enough or unlucky enough to end up in the water.
 
The two men stood at the stern holding long poles capped with video cameras. There were several beats of the kind of absolute silence that you hardly ever get in life, eerie moments when time seemed to stop and even the birds became quiet. Then, fifty yards away, the ocean swirled into a boil.
 
The dorsal fin of myth and nightmare rose from below and came tunneling toward them like a German U-boat, creating a sizable wake. The shark made a tight pass around the boat, pulling up just short of the stern. Its body, which was almost black as it broke the surface, glowed with cobalt and turquoise highlights underwater. “He’s coming up!” Peter yelled. The whaler rocked. A massive triangle of a head lifted out of the water and, in a surprisingly delicate way, bit the back corner of the boat. Scot leaned closer and filmed. The shark’s black eyes rolled; they could plainly see the scars all over its head and its two-inch-long teeth, backed by rows of spare two-inch-long teeth. Then, as quickly as it had come, the shark slipped beneath the surface, dove under the boat, and reemerged next to the seal. As the great white snatched the carcass, shaking it, bright orange blood burst from the sides of its mouth.
 
“It’s Bitehead!” Scot said. He broke into a full-face smile beneath his wraparound sunglasses.
 
“Ah, Bitehead,” Peter said. There was a moment of pleased recognition, as if greeting a fond acquaintance they had just happened to run into on the street. “We’ve known this shark for ten years.”
 
 
Every September, one of the world’s largest and densest congregations of great white sharks assembles in the waters surrounding the Farallon Islands, a 211-acre archipelago of ten islets in the Pacific, twenty-seven miles due west of the Golden Gate Bridge. No one fully understands what this gathering represents, why great whites, the ocean’s most solitary hunters, choose to reside for a period of time in such close quarters. What’s known for sure is that the sharks remain at this location for approximately three months. And this: having studied them for over a decade and a half in the Farallon White Shark Project, Scot Anderson and Peter Pyle have discovered that year after year, the same sharks return to exactly the same spot.
 
This annual reunion is at least partly about hunting. Despite strange inventories of items found in the bellies of sharks—a cuckoo clock, a fur cape, license plates and lobster traps, a buffalo head, an entire reindeer, and even, in one unlikely scenario, a man dressed in a full suit of armor—what great whites really love to eat are seals. And the Farallones are dripping with seals—northern elephant seals, harbor seals, fur seals, seals, seals, seals—all barking and bellowing, draped on the rocks like a blubbery carpet.
 
It wasn’t always this way. The islands’ seals, which once numbered in the tens of thousands, were hunted almost to extinction 150 years ago. Only after Southeast Farallon Island, the largest in the group, became a wildlife refuge in 1969 did the populations begin to recover. And as the seals returned, no one was happier to see them than the sharks. In 1970 Farallon biologists witnessed their first shark attack, on a Steller’s sea lion, a brawny animal that itself looks like a predator. During the next fifteen years, more than one hundred attacks on seals and sea lions were observed at close range. But the sharks were only warming up. By the year 2000, Peter and Scot were logging almost eighty attacks in a single season. Still, even accounting for the allure of a seal smorgasbord, why did these particular sharks keep returning? And why were they clustered together so tightly? No one had ever documented such behavior among great whites before.
 
Not that anyone’s had the opportunity. The Farallon Islands are the only place on Earth where it’s possible to study great white sharks behaving naturally in the wild. Unsubjected, that is, to the presence and fumblings of humans. In South Africa’s...