Oxnard , California ( CNN ) -- Thousands of strange sea creatures are washing ashore on California beaches , puzzling tourists and thrilling scientists quick to explain the phenomenon . `` The scientific name is Velella velella , '' said David Bader , director of education at the Aquarium of the Pacific in Long Beach , California . `` They 're jelly-like creatures , but they 're not exactly jellyfish . '' Also known as `` by-the-wind sailors , '' the creatures have a clear , distinctive fin sticking up from a blue , oval body no larger than the palm of a hand . `` Every now and then , the currents and the winds will change and these guys will , instead of being pushed out to sea , they actually wind up on the beach , '' Bader told CNN . They first started showing up in Washington and Oregon , and by mid-July reached San Francisco . On Thursday , photos turned up on Twitter from Hollywood and Silver Strand beaches in Oxnard . By-the-wind sailors do sting to catch their food , but humans need not worry . `` That sting is not very potent . It 's nothing that could actually get through my skin , '' Bader said while holding an assortment of the creatures . Velella velella feeds on plankton and fish eggs caught with tentacles that hang down from its jelly-like body . The creatures float on top of the ocean with their fins sticking straight up , leaving them at the mercy of the wind and the current . `` Out at sea , they look like bubbles on the surface of the ocean until you get up on them , '' said Julie Bursek of NOAA 's Channel Islands National Marine Sanctuary . They do n't live long on the shore , causing their deep blue color to fade until their clear , tougher fins are all that 's left behind . `` A lot of people probably never knew an organism like this existed in the world , '' Bader said . `` And you know the winds change , and all of a sudden they wash up on shore and we get to see what the ocean is really made of . '' 30 mesmerizing underwater photos .
These little sea creatures are called `` by-the-wind sailors '' ; the scientific name is Velella velella . The palm-sized creatures have a clear , distinctive fin sticking up from a blue , oval body . They first started showing up in Washington and Oregon . They are now being spotted on beaches north of Los Angeles .