Box jellyfish
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![Box jellyfish warning signpost at a Cape Tribulation beach in Queensland, Australia](/Images/godic/202501/07/Marinesting15708.jpg")
Box jellyfish (class Cubozoa) are cnidarian invertebrates distinguished by their cube-shaped medusae. Some species of box jellyfish produce extremely potent venom: Chironex fleckeri, Carukia barnesi and Malo kingi. Stings from these and a few other species in the class are extremely painful and can be fatal to humans.