Diving for abalone can be a dangerous sport, but that doesn't deter the thousands of people who trek to the northern California coastlines each season to take a stab at getting some of the prized mollusks.

With prices on the open market often reaching $125 a pound, the pull to the Sonoma and Mendocino county coastlines at the start of the season in April is strong.

On Sunday, not even two weeks into the start of the abalone diving season, a group of 10 friends renting a vacation home near Caspar Anchorage Bay in Caspar, California, set out to harvest the delicacy. Three of the men drowned, the first casualties of the season.

The men were diving for the mollusks when they found themselves in rough waves and became trapped in the surf of a narrow channel between two rock outcroppings, Mendocino Fire Capt. Sally Swan said. Witnesses described seven- to eight-foot swells.

It's not uncommon for people to travel for hundreds of miles each day to the rugged coast to go abalone diving and get their daily limit of three abalones. But they are often inexperienced and don't assess the danger associated with the treacherous sport, experts said.

"They're not going to go home empty-handed, so they make poor choices and dive without carefully evaluating the conditions, or worse yet, diving when the conditions are poor so they don't feel like they've wasted their time and gas money," said Chris Constantine, who has been diving for abalone for 15 years and publishes California Diver Magazine.

Scuba-diving tanks and gear are not permitted. Because the water ranges between 48 and 52 degrees year-round, a wetsuit, hood, boots and gloves are needed to keep warm. But neoprene suits are also very buoyant, so divers must wear a 20- to 30-pound weight belt to offset that buoyancy, Constantine said.

Low visibility in the water and sharks are other common dangers.

There isn't one agency that keeps statistics on abalone diving fatalities. But the hunt for the snail-like mollusks can be treacherous on the rugged coastline north of San Francisco. Each season is marked by numerous rescues and several fatalities.

Last June, an abalone diver fell to his death while climbing a steep cliff in Mendocino. The man had been diving for abalone when rough water may have pushed him and a friend into a cove not typically used by divers. Last November, a diver died in the water off the Sonoma County coast when he stopped breathing.

In May 2013, there were four deaths in eight days related to the hunt for shellfish off the coasts of Sonoma and Mendocino counties.

Not everyone who dies while diving for abalone drowns, authorities said. People have heart attacks, often caused by panic, freezing water or both. Others are killed when waves and surges toss them into the rocks.

What happened Sunday is not yet known as investigators continue their probe.

An off-duty firefighter who was fishing nearby saw the men struggling in the water and called for help.

The bodies of two divers were pulled from the water, and the body of a third man was found after sundown in a small cove after a nearly five-hour search, Swan said.

Crews on a rescue boat picked up two men who managed to get to a rocky area.

Authorities have identified the three men who died in the water as 49-year-old Tae Won Oh of Dublin, California and 49-year-old Hyun Kook Shin of Suwanee, Georgia. The third man, a 53-year-old man from New Jersey, has been identified, but his name was not released pending notification of his family.