The Portuguese man-of-war! At the moment, this is my muse; not a jellyfish but a siphonophore. Not the single creature it first seems to be, but a colonial organism made up of many individuals perfectly adapted to each other, unable to exist on their own.
This is a closeup of the tentacles of a Portuguese man o’ war. Unlike jellyfish, the man o' war is not a single organism, but a colony of four different kinds of smaller animals, called polyps and medusae, that have highly specialised body types to allow for very different functions, such as digesting and reproducing. Photo by Simon de Glanville