Siphonophore

Surprisingly this isn't science fiction...but a marvel from the ocean right here on planet earth. Siphonophores are creatures, actually they are a colony of creatures, belonging to the same family as corals, hydrids and jellyfish. They are composed of several separate zooids (individuals)that are either medusae or polyps. Medusae are basically jellyfish and polyps are basically sea anemone. Each zooid in the colony has a specialized function of swimming or eating. Neither can perform the other, they are entirely dependent on the colony.

All siphonophres are predators, capturing their prey with lures, similar to the anemone. The majority swim in the wide ocean and to feed cast a wide net of minute tentacles. One species tethers itself to the bottom, and the most common species, the Portuguese Man O' War drifts about on the surface of the ocean.

There are approximately 175 species, some specimens being the longest animals in the world measuring over 40 metres and are long and thin. Some have orange or red pigmentation but most are of a clear gelatinous material. Many of them are bioluminescent, glowing green or blue when disturbed.

Beautiful images of Siphonophores and other sea creatures from the Census of Marine Zooplankton. More detailed information and diagrams here.