Officials at Maine's most popular state beach posted signs last week that warn visitors the terrain beneath their feet could give way and land them in natural pockets of sticky sediment.
The signs at Popham Beach State Park, about 50 miles east of Portland, warn visitors of the potential hazards near the mouth of the Morse River, bureau spokesperson Jim Britt said by email.
The river meets the sea at the relatively bustling state beach, where Jamie Acord, a banking technology specialist, was walking on the first weekend of June when she instantly dropped to her waist in wet sediment, she said Tuesday.
"My husband turned around and went, 'Where'd you ... ,'" she recalled. "It's like if you were walking down the street and there was a missing manhole cover, but you didn't notice and you just dropped in."
Get top local stories in DFW delivered to you every morning. Sign up for NBC DFW's News Headlines newsletter.
Acord said she kept her wits and tried to figure out what happened. "I honestly thought I had fallen in a hole dug by a kid," she said.
But after she got out, it didn't look like the work of a child with a plastic shovel.
"When we turned around, there was nothing there — it was beach," Acord said. "It was very surreal."
U.S. & World
According to state documents, the hidden pits are the result of “supersaturated sand,” more commonly known as quicksand.
The episode shook Acord in other ways. She had items in her hands, and things might not have gone so smoothly if she hadn't had immediate help.
"I used to go to the beach by myself all the time," she said. "I might have began to panic because I couldn't get out on my own."
Acord worried about others who walk alone and might panic in such a situation. She said she spoke to a park ranger and a lifeguard before she told the world about the incident via social media.
The beach authorities explained that the nearby Morse River shifted closer to a well-trafficked part of the beach, putting visitors in the path of the unusually wet sand, Acord said.
A 2021 state guide to beach erosion said the river migrated a half-mile in the last few decades.
“The river underwent a dramatic course change in 2010,” wrote Robert G. Marvinney of the Maine Geological Survey, author of the guide.
The document, in part, blames climate change, and it says erosion from rising seas — the product of thermal expansion and melting ice sheets and glaciers — are redrawing the coastal map.
The shifting river brought with it subterranean water flow that can help create oversaturated pockets of sand on and near its banks, experts say.
At Popham Beach State Park and other beaches, wet sand is usually about 30% water, state marine biologist Peter Slovinsky said. The pockets of supersaturated sediment have about twice that amount of water, he said.
For now, beach visitors who end up in pits of wet sand are urged to stay calm; lose any extra weight from items, bags or unneeded clothing; spread their body weight as if they're trying to float; and crawl to safety.
Though the hazard in question is commonly referred to as quicksand, state officials made a point of saying it isn't the quicksand of Saturday morning cartoons.
People aren’t normally cemented into the depths below sea level. Slovinsky said falling into one of the pits is probably more common than we think because a lot of people walk it off and don't report it.
It happened to him, he said, teaching him that being calm is the best response. He advises that if a pit of wet sand absconds with any goods or clothing, don't be a hero.
"If your shoes come off, don't worry about it," he said. "Don't go after your shoes. Shoes can be replaced."
This story first appeared on NBCNews.com. More from NBC News:
