Thousands of bright-blue sea creatures known as
Velella velella, commonly called “by-the-wind sailors,” washed up on Baker Beach in San Francisco on Monday, covering stretches of sand beneath the Golden Gate Bridge.
The striking organisms, which look a bit like tiny jellyfish with translucent sails, are a common
sight on California beaches in spring and early summer. But when they
arrive in large numbers, they can transform a shoreline almost overnight.
Despite their jellyfish-like appearance, Velella velella are not true jellyfish. The National Park Service describes them as
free-floating hydrozoans, related to jellyfish, sea anemones and corals. They live at the ocean’s surface and drift with the wind, using a small, clear sail to move across the water.
That same sail is also what sends them ashore.
Thousands of bright blue Velella velella — commonly called by-the-wind sailors — washed up on Baker Beach in San Francisco on Monday, April 27, 2026, part of a seasonal phenomenon that can leave California beaches covered in the jellyfish-like creatures.
Aidin Vaziri/The Chronicle
“When the prevailing winds shift, such as during a storm, the Velella are driven towards the coast, where they often are stranded on beaches in great numbers,” Point Reyes National Seashore says on its website.
Once stranded, they don’t last long. As they dry out, the park service says, they become brittle and transparent, “looking like a cellophane candy wrapper.”
The Bay Area has seen big Velella wash-ups before. Scientists and park officials have long said the events are hard to predict, though they are most common when seasonal wind patterns push floating colonies toward shore.
The phenomenon has been showing up elsewhere in California. There were recently large beachings on
Central Coast shores, and vast numbers had been spotted offshore in the Santa Barbara Channel and on local beaches.
The creatures use stinging cells to catch plankton, but officials say they are generally not dangerous to people. Even so, beachgoers are advised to leave them alone and keep pets from eating them.
For anyone walking the coast, the display is vivid but brief. The blue soon fades. Within days, the creatures dry into pale, papery shells that are carried off by wind and waves.
Strandings of these jellyfish-like animals, sometimes called "by-the-wind sailors," usually mean spring is coming
www.smithsonianmag.com
While the arrival of Velellas isn’t unusual, previous
research has tentatively connected rising temperatures on the ocean’s surface with an increase in their strandings. “When we see signals coming from the ocean to the coast, we should pay attention,”
Julia Parrish, a marine biologist at the University of Washington, told
KQED’s Ezra David Romero in 2023. “The
Velella velella is an early warning bell that we may be seeing some shifts.”
