Those mysterious creatures along Huntington Beach’s coast are burrowing sea cucumbers

The pink gelatinous creatures that began washing up in Huntington Beach this week are burrowing sea cucumbers, according to a biology expert at UC Irvine.

The small pod-like critters, which slither and burrow into the sand, were seen along Huntington State and Huntington City beaches from late Monday into Wednesday.

Lifeguards in nearby Newport Beach said they had not seen any wash up in their area.

Matt Bracken, a professor at the department of ecology and evolutionary biology at UCI, said he initially thought the creatures were salps, barrel-shaped animals that look like jellyfish but have dorsal nerve cords. However, he took a closer look when he heard they were burrowing into the sand.

The creatures, which some beachgoers guessed were sea slugs or even alien embryos, are actually leptosynapta albicans, more commonly known as burrowing sea cucumbers. They’re typically found from Central California to Mexico.

“They commonly live burrowed under the sand and are occasionally displaced by surf and rainfall events like we had last weekend,” Bracken said.

Huntington Beach Marine Safety Lt. Eric Dieterman said large numbers of the creatures washed ashore Monday. By Wednesday, the number had dwindled significantly.

“They’ve made an appearance on our beaches before,” he said. “Not in this number, but I have seen them in the past.”

The animals are usually about 2 to 6 inches long and have 10 branched tentacles surrounding their mouths that they use to feed.

Lisa Mooney of Glendora said she was collecting seashells near the Huntington Beach Pier on Monday when she came across the creatures, which she thought were small jellyfish.

“There were so many along the sand you could barely walk,” she said.

Lifeguards also have faced a larger than usual number of stingrays close to shore in recent months.

hannah.fry@latimes.com

Twitter: @HannahFryTCN