Moon jellyfish have limited control over their movement, preferring to drift most of the time. However, they are also active swimmers and have an internal structure, called a hydrostatic skeleton, which helps them to move horizontally by body contractions and pulsations. The species swims to keep close to the water surface, where they spread their tentacles to catch food.
Moon jellyfish have specialized stinging cells called cnidocyte, which they use to capture prey and defend themselves against predators. Every cnidocyte contains a cnidocyst, a threadlike diminutive structure that produces a toxin that stings when in contact with the human skin. Cnidocytes are often located in the tentacles of the moon jellyfish.
The radial symmetry in the moon jellyfish is an adaptation present in other jellyfish species to sense both prey or the danger of predators in the same way on all sides. This adaptation is important in a slow swimmer like the moon jellyfish. In adulthood, the moon jelly fish has a transparent body with about 15 inches in diameter.
Like other jellyfish species, the moon jellyfish does not have a specialized respiratory system with gills or lungs. It also lacks excretory and circulatory systems. The body of the moon jellyfish is adapted to absorb the water oxygen by diffusion through its thin skin. Carbon dioxide and other waste materials is excreted through the same mechanism.