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Thousands of jellyfish washed up on the shore of Linda Mar beach in Pacifica on Memorial Day, eliciting screams from some and prompting some young wannabe scientists to dissect the creatures to figure out what was going on.

Tanya Schevitz took video of the gelatinous creatures, saying she thought it looked like there were "tens of thousands" of them, saying they looked like "bubbles of Jell-O" dotting the sand. On social media, people said they found swarms of jellyfish at Stinson and Rodeo beaches in Marin County, Poplar Beach in Half Moon Bay, and at Sunset Beach in Santa Cruz, over the long holiday weekend, too.

VIDEO: Thousands of jellyfish wash ashore in Pacifica

Most of them were dead on the beach, she said, but there were some that were alive. She said she saw a surfer got stung and some other people swimming at the beach also reported brushing into their tentacles. Her son dissected them to understand how they work while other children scream in the background. One man said he had never seen anything like that before.

Monterey Bay Aquarium Research Institute marine biologist Steven Haddock, the region's jellyfish expert, said there's nothing sinister going on; only that every so often, blooms of jellyfish wash up on shore because of the particular tide, current or wind gusts that day. He saw some in Santa Cruz himself over the weekend. The particular species he saw that washed ashore, Scrippsia, love kelp forests and are about the size of a baseballs with "frilly gonads."


The phenomenon has occurred before -- in Pacifica in 2004, and in 2010 and in 2004 along Ocean Beach in San Francisco, as just a few examples.

"Its just part of the natural dynamic," Haddock said. "For every one jellyfish that washes up on shore, there are 100 more swimming happily in the ocean."