Three divers die in separate drownings off California coast SAN FRANCISCO (Reuters) - Three recreational abalone divers died in separate drownings over the weekend in a 24-hour period along northern California's coast, police and coroner officials said on Monday. Diving for abalone, a prized mollusk, can be dangerous, but law enforcement officials said they knew of no other time when three people trying to catch them died in a single weekend. "It's very unusual," said Mendocino County Sergeant Scott Poma, the chief deputy coroner. The first death occurred on Saturday afternoon when Cedric Collett, 66, of the small northern California community of Pacifica, drowned off Shell Beach in Sonoma County, 85 miles northwest of San Francisco, county coroner spokesman Sergeant Greg Stashyn said. On Sunday morning, Kenneth Liu, 36, of San Francisco, drowned diving for abalone in the waters off the town of Jenner in Sonoma County, Stashyn said. And also on Sunday morning, Henry Choy, 50, of the San Francisco Bay area town of San Bruno, drowned in the ocean off Fort Bragg in Mendocino County, just north of Sonoma County where the other two deaths occurred, Poma said. A low tide brought large numbers of abalone divers to Mendocino and Sonoma counties over the weekend, Poma said. But in a sign of how rough the waters were for divers, it was too dangerous for rescue teams to enter the ocean for Choy, prompting authorities to call in a helicopter in an unsuccessful effort to save him, he said. All three divers had traveled to the coastal region separately to dive for abalone with friends, but all of them were alone when they drowned, officials said. "People really should be diving with partners who can help them," said marine biologist Carrie Wilson of the California Department of Fish and Wildlife. California state law prohibits abalone hunters from using scuba gear. As a result, they must either wade into the water or hold their breath while diving for abalone and their mother-of-pearl shells, Wilson said. "We've never allowed any scuba diving for abalone north of the Golden Gate Bridge, except for a short time during World War Two," Wilson said. That abalone population has survived because of that. The rules make diving for abalone "a dangerous sport," she said. Editing by Alex Dobuzinskis and Philip Barbara