Chironex fleckeri, commonly known as sea wasp, is a species of deadly venomous box jellyfish found in coastal waters from northern Australia to the Philippines. It has been described as the most lethal jellyfish in the world, with at least 63 known deaths in Australia from 1884 to 1996.

Notorious for its sting, C. fleckeri has tentacles up to 3 m (9.8 ft) long covered with millions of cnidocytes which, on contact, release microscopic darts delivering an extremely powerful venom. Being stung commonly results in excruciating pain, and if the sting area is significant, an untreated victim may die in two to five minutes! The amount of venom in one animal is said to be enough to kill 60 adult humans (although most stings are mild). ...