A cousin of the jellyfish, the V. velella are in the cnidarian family, a phylum containing about 9,000 species of marine aquatic invertebrates. However, that doesn't mean that velellas are anything like jellyfish. "In terms of taxonomy," Jim Watanabe, a marine ecology and invertebrate zoology lecturer at Stanford University’s Hopkins Marine Station, told SFGate, "they are as different from jellyfish as mammals and birds would be among vertebrates."
Instead of living underwater like jellyfish do, velellas inhabit the surface and use their tentacles to reach into the water to catch their food, which includes fish eggs and other tiny sea organisms. The V. velella are also completely harmless to humans — another distinction from their poisonous cousins.
Velellas also have fins on their bodies that act like sails, taking them wherever the wind blows. For this reason, they are sometimes called by-the-wind sailors. And it might be strong wind patterns that have beached them by hordes along the Northern California coast.
Beachgoers have been snapping pictures of these beautiful creatures and posting them on social media. A catch: They may be gorgeous, but velellas can't survive out of the water.
"If you pick these guys up and put them in the water and look at the under side, [you'll see] these tiny little tubular polyps and tentacles and other sort of things, which is the living part of the animal," Watanabe said. "If it isn’t face-down in the water then they can't make their living — they'll dry out on beach quickly."