The Blue Button jellyfish, or Porpita porpita, is not actually a jellyfish at all. It's a community of organisms working ...

San Diego beaches are awash with small, blue, jellyfish-resembling creatures known as Velella velellas. Why it matters: Despite their appearance, Velella velellas aren't in the same group as ...

This story appears in the October 2018 issue of National Geographic magazine. Moon jellies, which are found in shallow bays around the world, look like small, not entirely friendly ghosts.