what has 4 brains, 24 eyes, and can kill you in a minute flat?

The deadly Chironex fleckeri jellyfish, of course, as reported in the June issue of the Smithsonian Magazine.

Most jellyfish are passive; they drift up and down in the water column, or are pulled to and fro by the tides and winds. They float through the oceans devouring tiny fish and microscopic creatures that bumble into their tentacles, and are no threat to humans. But those known as box jellyfish, for the shape of their bell, or body, are a breed apart. Also called cubozoans, they're voracious hunters, able to chase prey by moving forward—as well as up and down—at speeds of up to two knots. They range in size from the various irukandji species to their big brother, the brutish Chironex fleckeri, which has a bell the size of a man's head and up to 180 yards of tentacles, each lined with billions of cells bursting with deadly venom.

"A Chironex fleckeri can kill a human in one minute flat," says Jamie Seymour, widely considered the world's foremost box jellyfish researcher. The most recent victim was a 7-year-old boy who died two years ago at a beach south of Cairns, becoming one of about a hundred people believed to have been killed over the past century by Chironex in Australia alone. "Chironex is by far the world's most venomous creature," says Seymour. "It makes venomous snakes look like amateurs."