No one could even remember a shark attack along this resort-studded stretch of Mexican coast popular with surfers and Hollywood's elite. Many of the large predators had been pulled from the ocean by fishermen.
So when sharks attacked three surfers in less than a month, two fatally, it was unthinkable.
The latest attack came Saturday, when a shark chomped down on the arm of surfing enthusiast Bruce Grimes, an American expat who runs a surf shop in Zihuatanejo.
Grimes and a handful of other surfers were out on dark, choppy waters when he felt something lift his board. He managed about five strokes before teeth sank into his arm. "Shark!" he screamed, wresting his arm back. Grimes made it to shore, escaping with a few gashes.
"There wasn't any time to panic," he said. "I thought: 'Don't want to die. Don't want to lose my arm.'"
Only later did the 49-year-old Florida native learn a local surfer had been killed by a shark at a neighboring beach the previous day. Less than a month before that, a visitor from San Francisco was killed while surfing another nearby beach.
Before that, shark attacks were unheard of here. University of Florida expert George Burgess was in the area Wednesday interviewing witnesses, going over autopsy reports and checking out beaches to find out why the sharks had suddenly become so aggressive.
Burgess' International Shark Attack File records an average of only four fatal shark attacks around the world each year. This year, there has been only one other recorded shark fatality outside Mexico — a 66-year-old surfer killed at Solana Beach, Calif.
The attacks around Zihuatanejo have puzzled experts and, alarmingly for local businesses, the mayhem is keeping tourists away.
After the first fatality, panicked officials strung lines of baited hooks offshore and slaughtered dozens of sharks, drawing international criticism. Authorities planned to meet Thursday to seek Burgess' advice.
Marine biologist Chris Lowe, who runs the shark lab at California State University, Long Beach, said there is little officials can do beyond trying to keep people out of the water and studying why sharks have suddenly turned so aggressive. Hunts don't usually help, he said.
Lowe also said officials should keep the attacks in perspective.
"People have a much better chance of dying of food poisoning going to Mexico than being bitten by a shark," he said. "It's far more dangerous driving to the beach than it is getting in the water."
The International Shark File has found that attacks have been increasing over the past century, mostly because of the growing popularity of water sports like surfing.
That's part of the reason experts say shark hunting is futile: Even as shark populations are declining, the number people swimming in the ocean is increasing.
"Finding the killer shark is nearly impossible," said Jose Leonardo Castillo, the chief shark investigator for Mexico's National Fishing Institute.
Mexican experts are planning a catch-and-release study to determine the species of sharks that has been attacking. And maritime officials, stung by the backlash over the shark hunt, have switched to conducting sea and aerial patrols to watch for sharks near shore.
After repeated appeals by environmentalists, officials have promised to post large warning signs on beaches where sharks have attacked — a dreaded prospect for some in the surfing business.
"Those signs will be the worst thing for us," said Herberto Perez Yanez, who teaches surfing and rents out boards at Troncones beach, where 24-year-old Adrian Ruiz of San Francisco was killed April 28.
"Plenty of fishermen out here hunt sharks, and no one says anything. The ecologists say they don't want the hunt, but they're just sitting in their offices while we have to be here," he said.
Perez Yanez was interviewed while giving surfing lessons to a couple from Texas — the only two people in the water at Troncones and his first clients since Ruiz died. He usually teaches three groups a week.
Lisa Rabon, of Walnut Springs, Texas, said she and her husband came to celebrate her 50th birthday and fulfill her lifelong dream of learning to surf. She didn't learn of the attacks until after arriving and said she has seen hardly anyone else in the water.
"I've been hearing about the attacks, but I didn't ask for any details. I didn't want it to be part of my experience," she said. "If I think about sharks, I'll never learn."
Leon Perez Yanez, brother of Herberto and president of the Guerrero state surfers association, said at least three groups canceled surfing lessons with him since the weekend attacks.
Grimes said he was worried about his own business — a surf shop he opened six months ago when he decided to move to Zihuatanejo permanently after 25 years of visiting.
But he said he will soon be back on his board, and is sure most surfers won't stay away long because they accept the risks of their sport.
"I'll go right back. Yeah, I'm that stupid," Grimes said, examining his bandaged arm outside the hospital where he just had his daily cleaning. "I'll go right back out as soon as I'm able to."
That is part of the problem, said Lowe, an avid surfer himself. With more people in the water, in more remote locations, attacks are inevitable.
"For every shark we take out of the water, we put 10 people in," he said. "The bottom line is the ocean is a wild environment and people just have to accept the risks when they go in it."