Thousands of mysterious jellyfish-like creatures wash up on California shores

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Human-sized jellyfish lurking off English coast stuns divers

A human-sized jellyfish lurking off the coast of the English Channel stunned divers who said, ‘it’s an experience we’ll never forget.’

Southern California beachgoers may notice a plethora of jellyfish-like creatures washed up on local shores – but sea jellies these blue blobs are not.

Thousands of Velella velellas, or by-the-wind sailors, have recently emerged on Golden State beaches from San Diego to Marin County. Pictures taken on April 28 in San Clemente show thousands of gelatinous hydrozoans strewn across a single beach.

Point Reyes National Seashore, a National Park Service (NPS) preserve located in the Bay Area, addressed the "blue tide" in a Facebook post last month.

"During spring and early summer months, Point Reyes seaside visitors may come across thousands of by-the-wind sailors (Velella velella) stranded on the beach," the post read.

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Thousands of dead "by-the-wind sailors," whose scientific name is Velella velellas, have been washing up on shore in recent days across Southern California. (Laylan Connelly/MediaNews Group/Orange County Register via Getty Images)

"These blue jellyfish-like creatures use their translucent, triangular sails to free-float around the ocean," Point Reyes explained. The cnidarians do not actively navigate, but rather flow whichever way the wind takes them. Unlike jellyfish, they cannot swim against ocean currents.

"Their sailing routes are determined by prevailing winds, and a shift in these breezes can spell bad news for these little seafarers – if the wind is too strong in the wrong direction, they can get blown onshore and will die," Point Reyes explained.

After a few days of being on shore, the bodies of velellas will decompose, which leaves "just their cellophane-like sail and floats," according to Point Reyes. The aquatic animals are also susceptible to being eaten by predators, but lucky ones may be pulled back into the ocean's tide before dying.

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The myriad of velellas washing ashore may be related to rising ocean temperatures. (Laylan Connelly/MediaNews Group/Orange County Register via Getty Images)

The creatures often dine on plankton, which they catch with their stinging tentacles. The NPS says that its stingers are rarely harmful to humans, making them relatively safe for beachgoers to pick up.

Researchers believe that the recent sightings are related to warmer currents in the waters off California, which can increase wind speeds. When velellas washed ashore last spring, oceanographer Anya Stajner told FOX 5 San Diego that the creatures are "sort of like San Diegans."

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Velella velellas, or by-the-wind sailors, have recently washed up on beaches from San Diego to Marin County in the Golden State. (Laylan Connelly/MediaNews Group/Orange County Register via Getty Images)

"They spend a lot of their time in the sun, and they go wherever the breeze blows them," she laughed. "They’re kind of what I would consider an ephemeral species – a little bit rare and exciting to come across."

"Because they live at this air and water interface, they pretty much sit exactly at the surface of the water," Stajner added. "They just go where the wind blows them. And that’s actually why they end up on our shores sometimes … they get pushed by a strong breeze that they can’t escape."

Despite resembling jellyfish, Velella velellas are a different species that live on the ocean's surface. (Laylan Connelly/MediaNews Group/Orange County Register via Getty Images)

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Fox News Digital reached out to Point Reyes for comment.

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