The most venomous creature of the sea is on the move and spreading across the oceans leaving a trail of baffled scientists and poisoned victims. These gelatinous monsters, which have been known to kill within three minutes, have been part of the ocean's ecosystem for more than 500 million years. However, changes to the seas and global warming may mean that mankind himself is creating this population explosion. Blooms of these floating death traps have been reported from New York's Hudson River to the beaches of Spain and have even shut down a nuclear power station in Japan. While little is known about many jellyfish species, new research is unravelling some frightening details: these creatures are not simply drifting blobs, but have an intelligence that proves that they are an apex predator of the sea.