What are jellyfish? The term jellyfish generally refers to the umbrellashaped gelatinous zooplanktons that belong to Scyphozoa (true jellyfish), Staurozoa (stalked jellyfish), Cubozoa (box jellyfish), and Hydrozoa of Phylum Cnidaria. Their sizes, shapes, and habitats are diverse. Sexually mature jellyfish range from millimeters to meters in diameter, and they can be found almost anywhere in the...