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Entry 462Filed under Breeding

Why Blue Sea Creatures Are Washing Up on California Beaches

The blue colonies washing up on California beaches are Velella velella, wind-driven relatives of jellyfish. Here’s why they strand and how to handle them safely.
3-minute read By Animalso Team
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The blue creatures washing up on California beaches are Velella velella, commonly called by-the-wind sailors. They are colonial relatives of jellyfish—not true jellyfish—and their small sails let wind and currents carry them across the ocean surface. When winds push large offshore patches toward shore, the animals can blanket beaches. They are generally not dangerous to people, but live specimens can sting, so leave them alone and keep them away from pets’ and children’s mouths and eyes.

What are the blue blobs on California beaches?

They are Velella velella, or by-the-wind sailors. Each visible animal is a colony of specialized individuals living together, rather than a single conventional fish or jellyfish. The National Park Service describes them as related to jellyfish but “not true jellyfish.”

A by-the-wind sailor is a flat, oval, bluish-to-purple colony, typically three to four inches long, with a flexible triangular sail about two inches high. The sail sits diagonally on a gas-filled float. Beneath it are a mantle, feeding tentacles and a central mouth; the blue tentacles contain stinging cells that catch planktonic prey.

Why do they wash up in such large numbers?

By-the-wind sailors live at the ocean surface offshore and cannot steer themselves against the wind. A change in prevailing winds or a storm can drive broad surface patches toward land, where the colonies strand. Spring upwelling brings cold, nutrient-rich water that supports phytoplankton and zooplankton—the food supply for these colonies. Depending on wind conditions, a beaching event may last days or weeks.

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In a March 15, 2025 incident report, NOAA said a suspected pollution sighting off Stinson Beach was instead “biogenic”—masses of jellyfish-like creatures, identified in that incident sentence with the spelling “Vellela velella”—and not a pollutant. The accepted spelling is Velella velella.

Where are California sightings happening?

KQED reported abundant 2026 sightings at Baker Beach, Crissy Field and Ocean Beach in San Francisco, as well as around Santa Cruz, Pescadero and Bodega Bay. Exact locations and duration change with winds, so a list of affected beaches is only a snapshot, not a forecast.

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UC Davis Bodega Marine Reserve research coordinator Jackie Sones told KQED that “beaches in this area appear blue from a distance because of the numbers of Velella right now.” The color comes from the many blue-purple colonies together, rather than a change in the sand or a spill.

Does the recent increase mean their population is growing?

A 2026 synthesis by Cimino and coauthors, published in the Journal of Plankton Research and deposited in a NOAA repository, compiled observations from about 1900 through 2025. It reported unprecedented numbers of strandings and at-sea observations since 2014, but found no consistent association with El Niño.

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The authors discuss several possible explanations, including larger populations, larger surface patches, or stronger transport toward shore. The observations do not establish one cause, so a beach full of by-the-wind sailors should not be taken on its own as proof of a population surge or an El Niño effect.

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Can you touch them, and are they dangerous to pets?

The National Park Service says their stinging cells are rarely harmful to humans, but live animals can sting. The Natural History Museum advises leaving them where they are; stranded colonies are unlikely to survive. Avoid handling them, and do not let children or dogs put one in their mouths. After accidental contact, do not rub your eyes or face.

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For a pet that has mouthed one, prevent further contact and watch for signs of irritation or distress; contact a veterinarian if symptoms occur. The safest choice for people and animals is to observe from a distance and leave the colonies on the beach.

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