Box Jellyfish Quick Facts

Box jellyfish are a diverse group of cube-shaped jellyfish in the class Cubozoa. Use these concise facts as a starting point, then follow the links for detailed, sourced explanations.

15 box jellyfish facts

1. “Box jellyfish” is a group, not one species. The name refers to the class Cubozoa.
2. Their bell is roughly cube-shaped. This is the feature that gives the group its common name.
3. Only some species are life-threatening to people. Most cubozoans are not known to cause fatal human envenomation.
4. Chironex fleckeri is the best-known dangerous species. It occurs in tropical northern Australian waters and parts of the Indo-Pacific.
5. Large Australian box jellyfish can have up to 60 tentacles. Tentacles grow in groups from the lower corners of the bell.
6. The bell of Chironex fleckeri can reach about 30 centimetres. Its tentacles may extend as far as three metres.
7. Many box jellyfish have 24 eyes. The eyes are arranged in four sensory structures called rhopalia.
8. Some of the eyes have lenses. They are more structurally complex than simple light-sensing spots.
9. Box jellyfish can swim directionally. They do more than drift passively with currents.
10. They are active predators. Prey can include shrimp, prawns, and small fish.
11. Their tentacles contain nematocysts. These microscopic stinging cells deliver venom when triggered.
12. Severe stings can affect breathing and the cardiovascular system. Extensive contact with a dangerous species is a medical emergency.
13. Some small box jellyfish can cause Irukandji syndrome. Severe symptoms may be delayed after a mild initial sting.
14. Distribution and season vary by species. Local beach warnings are more reliable than a universal “jellyfish season.”
15. Prevention works. Patrolled beaches, stinger suits, designated swimming enclosures, and compliance with closures reduce risk.

Continue learning

• Complete box jellyfish guide
• Appearance and identification
• Vision and eyes
• Diet and hunting
• Life cycle and reproduction

Sources

• Australian Museum: Box Jellyfish
• NOAA National Ocean Service: Box jellyfish
• Healthdirect Australia: Jellyfish stings

Editorially reviewed: 22 August 2026.

Go beyond the quick facts

For the full scientific and safety overview, read the complete box jellyfish guide. You can also inspect the authorities and primary studies in our research and source library.