They are iridescent, bright blue and jellylike, with stinging tentacles that dangle from their flat, oval-shaped bodies. Just three to four inches long, these alien-looking creatures use a short, clear flap of skin to catch gusts of wind, propelling them through the ocean.<\/p>\n
That flap, or sail, is how they got their nickname, \u201cBy-the-Wind Sailors,\u201d but it is less helpful when the creatures are stranded by the thousands on California beaches, as they are now.<\/p>\n
In the past few days, nature aficionados and everyday passers-by alike have reported the phenomenon, posting photos of the invasion on social media<\/a> and on biodiversity-spotting websites<\/a>.<\/p>\n The marine carnivores, whose scientific name is Velella velella, are not quite jellyfish but are closely related. They appear every spring and have been doing so for \u201cmillions of years,\u201d said Steven Haddock, a marine biologist at the Monterey Bay Aquarium Research Institute. But every few years (including this one), when especially strong winds blow in the right direction, millions of them can wash ashore in droves, \u201cspanning from Baja California to Alaska,\u201d he said.<\/p>\n This year, they\u2019ve been spotted along the coasts of Washington and Oregon, although a majority of sightings so far have been in California.<\/p>\n Despite the velella\u2019s stingers, those who stumble upon them have no need to worry, Mr. Haddock said. They\u2019re not likely to sting a human who picks them up by their sail.<\/p>\n \u201cPeople may have never seen that many jellylike things washing up on the beach, but it\u2019s really not cause for alarm,\u201d he said.<\/p>\n Usually, they live near the ocean surface, where they can bunch together by the thousands. Mr. Haddock said that at times, they accumulate in such a way that if you\u2019re on a boat and see a colony, it would appear as if you could step out and walk across them.<\/p>\n