It could easily have been the role model for the terrifying creature in the film 'Alien'. A perfect toxin-loaded killing machine, there is no creature on earth that can dispatch a human being so easily or so quickly. The box jellyfish is so packed with venom that the briefest of touches can bring agonising death within 180 seconds. And if comes under sustained attack it responds by sending its compatriots into a super-breeding frenzy in which millions of replacements are created. The really bad news is that the box jellyfish and another equally poisonous species, Irukandji, are on the move. Scientists are warning that their populations are exploding and will pose a monumental problem unless they are stopped.