The North Coast beach that produced a sleeper wave Sunday that swept a little girl to her death in the ocean and claimed the life of a young woman who tried to save her was the site of another double drowning a few years ago.

A similar incident occurred at Freshwater Lagoon Beach in January 2004 when a so-called sleeper wave grabbed an 8-year-old boy and a 13-year-old girl. The girl was saved; the boy drowned. The boy's uncle died trying to save him.

About two years ago, a powerful wave drowned yet another child 4 miles away at a beach near Stone Lagoon, north of Arcata in Humboldt County, according to Charlie Van Buskirk, a deputy coroner for Humboldt County.

"The ocean is unpredictable and unforgiving," he said. "It's not something to have a cavalier attitude about. When I go out, I don't turn my back on the ocean."

Sleeper waves, which can unexpectedly break on shore or quickly inundate a dry beach with a foot or two of powerful current, are a dangerous staple of Northern California's rugged shoreline. Each year or so, such waves are blamed for the drowning deaths of a few people along the North Coast, from Marin County to Oregon.

Freshwater Lagoon Beach is on a spit of land where Redwood Creek flows into the ocean near the town of Orick, about 30 miles north of Arcata. With its huge waves and riptides, the beach has a reputation of such treachery that even die-hard surfers stay away.

Sunday's incident occurred at about 11:20 a.m., authorities said.

It was a warm, sunny day. Four-year-old Mikayla Tingey was on a camping trip with her 28-year-old mother, Brandy Tingey, and her mother's friend, 21-year-old Jeanne Wood, all of Elk Grove in Sacramento County.

The three had stopped off to visit the Redwood Creek picnic area, a National Park Service day-use facility that has access to Freshwater Lagoon Beach. The popular beach, which is nestled next to small sand dunes, is about a 1/2-mile long.

Amy Caldwell, the acting superintendent of Redwood National and State Parks, said that Freshwater Lagoon Beach is posted with signs that warn of dangerous waves, currents, and undertow. There are no lifeguards. The water is very cold, and anyone entering the water without a wetsuit is subject to hypothermia quickly setting in.

"It's not a safe area for swimming at all," Caldwell said. "There are heavy riptides there. There is an undercurrent. ... As far as we know the child wasn't even in the water. It was a sneaker wave that got her wet and carried her away. She was playing with her mother on dry sand."

Wood, a friend of the child's mother, jumped in and grabbed the girl, but the two were quickly dragged into the ocean, Van Buskirk said. The girl's mother made two attempts to rescue her daughter and Wood, and was also pulled into the surf but was able to pull herself out.

"The mother did go back on shore to remove her cargo pants and re-enter the water," Caldwell said. "I guess she realized she couldn't save the child."

A Coast Guard helicopter and rescue boats were dispatched, and Wood's body was recovered in about an hour. Mikayla Tingey's body was found two or three hours later, a half-mile from the shore.

Brandy Tingey spent Sunday evening holding the body of her deceased child in the hospital.

"She's stunned," said Van Buskirk, adding that relatives flew up to comfort Tingey. "I don't think they could have outrun the wave. Things happen so fast ...

"The mother said at one point that she thought she was going to die in the surf because they were getting tumbled around in it. And when she dragged herself out of it, she knew that she would be the only one to survive."

On Jan. 2, 2004, two sisters and their families from the Northwest were traveling north on Highway 101, returning from a trip to Disneyland, and stopped for lunch at Freshwater Lagoon Beach.

A sleeper wave knocked over an 8-year-old boy and a 13-year-old girl. The boy drowned. His uncle, Jeffrey Glenn Russell, 38, of Tacoma, Wash., died trying to save him. Russell's 13-year-old daughter was saved by another relative.

"When it's a nice, calm day people tend to underestimate the power of the ocean," Caldwell said. "The ocean is a treacherous place... Sneaker waves happen quite frequently. They're very powerful and can easily take people out very unexpectedly."

• San Francisco Chronicle