<P> See text . </P> <P> Jellyfish or jellies are softbodied, free - swimming aquatic animals with a gelatinous umbrella - shaped bell and trailing tentacles . The bell can pulsate to acquire propulsion and locomotion . The tentacles may be utilized to capture prey or defend against predators by emitting toxins in a painful sting . Jellyfish species are classified in the subphylum Medusozoa which makes up a major part of the phylum Cnidaria, although not all Medusozoa species are considered to be jellyfish . </P> <P> Jellyfish are found in every ocean, from the surface to the deep sea . Scyphozoans are exclusively marine, but some hydrozoans live in freshwater . Large, often colorful, jellyfish are common in coastal zones worldwide . Jellyfish have roamed the seas for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal . </P> <P> The popular English name jellyfish has been in use since 1796 . It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, free - swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes". Even some scientists include the phylum ctenophora when they are referring to jellyfish . Other scientists prefer to use the more all - encompassing term gelatinous zooplankton, when referring to these, together with other soft - bodied animals in the water column . </P>

What kind of water do jellyfish live in