Jellyfish are typified as free-swimming marine animals and the major non-polyp form of individuals of the phylum, Cnidaria.
They have roamed the seas for at least 500 million years, possibly 700 million years or more. This makes them the oldest multi-organ animal we know of. They consist of a gelatinous umbrella shaped bell with trailing tentacles. The bell can pulsate for locomotion while stinging tentacles are used to capture prey.
Jellyfish, also known as “jellies” are found in every ocean, from the surface to the deep sea. Most are exclusively sea water, but some Hydrozoans live in freshwater. Large, often colorful jellyfish are in the coast zones worldwide.