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Jellyfish are so jelly-like primarily because their bodies are made up of a soft, gelatinous substance called mesoglea, which is mostly water. The jelly-like consistency of a jellyfish is a result of this material, which can be up to 95% water. The mesoglea is sandwiched between two layers of cells: the outer layer called the epidermis and the inner layer called the gastrodermis.
The mesoglea gives jellyfish their buoyant property, allowing them to float and move with the currents of the ocean with minimal energy expenditure. Jellyfish do not have bones or a hard exoskeleton; their soft bodies make them extremely flexible and able to squeeze through tight spaces. The absence of rigid structures also reduces their need for food, as they do not need to produce energy to maintain a skeletal system.
Jellyfish have muscle fibers within the mesoglea and alongside the epidermis, which they can contract to change their shape. This contraction squeezes water out of the bell, propelling them through the water. Despite their simple body structure, jellyfish are effective predators, using their tentacles and their jelly-like bodies to capture and consume prey