Jellyfish or jellies are free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for pushing forward, while stinging tentacles can be used to capture prey.
Jellyfish are found in every ocean, from the surface to the deep sea. A few inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The have roamed the seas for at least 500 million years making them the oldest multi-organ animal.