A jellyfish has no eyes, ears, nose, brain or heart. In fact, a jellyfish has no head or bones of any kind and is made almost entirely of water.
Jellyfish are not actually fish, but relatives of corals and sea anemones. Scientists believe they got the name jellyfish from their jelly-like, gooey bodies. They are classified as invertebrates because they do not have a backbone or spine.
Jellyfish live in every ocean on the planet and come in a large variety of types, colors and sizes. Most jellyfish have tentacles that they use to sting predators and catch tiny fish and plankton to eat.