Gooey blue blobs are washing up on U.S. beaches—here’s why

This spring, beaches from California to Washington have become clogged with small, squelchy electric blue animals—piled up several inches deep in some places—accompanied by a dubious smell. 

These jellyfish-like creatures float along the ocean surface using their tentacles to feed on plankton below. But sometimes certain ocean conditions force huge masses of them onto land. 

So, what are these creatures and why have they recently flooded the western U.S. coastline? Here’s everything you need to know. 

What are Velella velella?

Known as by-the-wind sailors because of the way they catch the ocean breeze using the sail-like fin on top of their bodies, Velella velella are stinging animals closely related to jellyfish, sea anemones, and coral. While often confused with jellies, these gelatinous blobs are not true jellyfish. 

“Velella velellas are a type of zooplankton, which is basically an animal drifter that can’t swim against horizontal currents in the ocean,” says Anya Štajner, a plankton ecologist at Scripps Institution of Oceanography. “I always say they're the zooplankton so nice they named it twice.” (Velella comes from the Latin word vēlum, or ‘sail’).

Each of these cerulean organisms is not a single animal, but instead a colony of thousands of polyps, called zooids, all working together. Each type has a specific task: stinging polyps (dactylozooids) catch prey, feeding polyps (gastrozooids) digest the food, and reproductive polyps (gonozooids) create more sailors. Their cobalt hue camouflages them against the water and may act like sunscreen, protecting them from the sun’s UV rays.

To move around the ocean’s surface, they hitch a ride on winds and currents. “They have a chitinous sail that sticks up above the water column,” she says. “This allows them to get pushed around by the breeze—hence how they get their nickname, by-the-wind sailors.”

Mass strandings 

Velella strandings don’t ripple along the coast like a crowd doing the wave at a stadium. They hit all at once. “What that means is that there's this humongous mat or set of mats of Velella offshore all up and down the coast,” says Julia Parrish, a marine ecologist at the University of Washington. 

In a 2021 study, Parrish and colleagues investigated what conditions result in mass strandings. Firstly, winds must blow predominantly to the east to push things floating on the surface onto shore. These westerly winds happen every spring, but they don’t bring these tiny voyagers every year. “The wind's blowing in the right direction, but sometimes they're not there to be blown in,” she says. Conditions out at sea must have allowed enough of these gelatinous creatures to bloom for them to be washed ashore in such vast numbers.

The water must also be warmer than usual, which might explain why so many washed up this year. “There's a humongous tongue of warmer-than-normal water that's licking up from the equator,” she says. March 2026 was the warmest March in the U.S. in 132 years, likely due to climate change. Parrish and colleagues also theorize that “a milder winter—a less stormy winter—will tend to allow more of those colonies to survive over the winter,” meaning there are more to strand in spring. 

The number of sailors washing up varies. “Sometimes you get them just polka-dotting on the sand,” says Štajner, but other times beaches can be “thick with them.” Recently, in San Francisco Bay, “you couldn't take a step without stepping on top of them,” she recalls. 

When lots of these “little sails” wash up simultaneously, an unpleasant, fishy stench pervades the shoreline. That’s to be expected with a mass marine animal stranding, says Štajner: “There's going to be an associated smell—maybe a little extra beachy.”  

Although by-the-wind sailors use stinging cells to catch prey, their stingers don’t hurt humans—but be careful before you pick one up, as they look similar to Portuguese men-of-war: “A Portuguese man-of-war will sting you and it will be nasty,” Štajner says. 

Recently, Štajner collected specimens from the strandings and examined them under the microscope. She could even see the tiny algae that lives inside the sailors’ tissue. Just as corals get energy from microalgae living in their bodies, this provides Velella with extra food when prey is scarce. “If you think of a by-the-wind sailor that's at the whim of the wind,” says Štajner, “you might get pushed away from your food source.” 

How strandings impact the ecosystem 

By-the-wind sailors provide food for animals including bubble snails, blue dragon sea slugs, and fish. “We’ve observed Mola mola, which is the ocean sunfish, pulling up to these big Velella blooms and just popping them like candy,” says Štajner. 

When they wash up onshore, the carbon, nitrogen, and nutrients stored in their bodies is also brought onto land. Exactly what impact this has on the ecosystem is not yet clear. A single Velella is “a little wispy bit of a thing,” says Parrish, “but there are so many of them. So that transfer of biomass may be substantial. It's really hard to know.”

But these jelly-like organisms quickly dry up. Eventually crispy like potato chips, they seem to be an unappealing food source for terrestrial animals such as seabirds. “It would be like chewing on your fingernails,” says Parrish. “You're not going to get a lot of nutrition.”

Exactly what’s going on remains to be seen. Scientists are still trying to collect and analyze data to understand the finer details behind why strandings happen and exactly how they might impact the environmental. 

Learning how big the creatures are when they wash up could tell scientists how old they are and, therefore, where they came from, says Parrish.

Štajner also wants to use by-the-wind sailors as “gateway zooplankton” to get people interested in lesser-known sea creatures: “These wash up on shore and then people become curious about what they are and what other things are out there.”