Box Jellyfish (Cubozoa)

Box jellyfish, the cubozoans, look like ordinary jellyfish but swim fast, maneuver around obstacles and see fairly well despite having no brain. They are told apart from the true jellyfish, the scyphozoans, by a square shape when viewed from above, four evenly spaced tentacles or bunches of tentacles, and well-developed eyes. Few fossil cubozoans are known, and about 20 species are known today, living in tropical and semitropical waters. The Australian stinger Chironex fleckeri is among the deadliest creatures in the world and has caused human fatalities.