Identification comparison · Last reviewed 22 August 2026
Box jellyfish and moon jellyfish are both cnidarians, but they belong to different classes and move through the sea in very different ways. The quickest visual contrast is a cube-like, purposeful swimmer versus a round, saucer-like drifter with four horseshoe-shaped gonads often visible through the bell.
| Feature | Box jellyfish | Moon jellyfish |
|---|---|---|
| Class | Cubozoa | Scyphozoa |
| Bell | Roughly four-sided | Round, shallow saucer |
| Eyes | 24 eyes on four rhopalia in many species | Simple light-sensing structures |
| Swimming | Strong jetting and active steering | Rhythmic pulsing, more influenced by currents |
| Sting | Ranges from mild to life-threatening by species | Usually mild to people, though reactions vary |
Do not identify by danger
A painful sting does not prove the animal was a box jellyfish, and a transparent bell does not rule one in. Regional species, tentacle pattern and a clear photograph are more useful.
Four circles versus four corners
The four pale or purple horseshoes visible in many adult moon jellies are reproductive organs inside a circular bell. They are not the four corners of a cube. A box jellyfish’s tentacles emerge from muscular pedalia at the lower corners.
Sources
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See an error or outdated source? Read our corrections process. Safety information is educational and does not replace local emergency services or clinical advice.
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