The name "irukandji" was first applied only to the syndrome caused by the jellyfish Carukia barnesi, but in the absence of a common name for the creature, the word has also come to mean the jellyfish itself. It is a small jellyfish (around 2cm diameter bell) responsible for an unusual and dramatic syndrome observed following stings.It occurs in northern Australia, especially north Queensland. Unlike box jellyfish, Irukandji are found mostly in the deeper waters of the reef, although they may be swept inshore by currents. Divers and snorkellers are particularly at risk. Stings have been recorded around the northern coast from Childers in Queensland to Broome in Western Australia, and a similar syndrome has been described elsewhere in the Pacific.
Many people have been affected, including several hundred in north Queensland in the summer of 1991/92. Every summer, more than sixty people are hospitalized with this potentially fatal syndrome. Recent research has shown that another two similar species of carybdeid jellyfish, Carukia shinju and Malo maxima, are found in Australian coastal waters. These may also be dangerous to humans.