Dangers on the Reef: Irukandji Jellyfish Unlike Chironex fleckeri (Box Jelly Fish), Irukandji are found mostly in the deeper waters of the reef, although they may be swept inshore by prevailing currents. Divers and snorkellers are particularly at risk. http://www.barrierreefaustralia.com/the-great-barrier-reef/irukandji.htm
