The box jellyfish's venom can instantly stun or kill prey, it's considered to be one of the deadliest, containing toxins that attack the heart, nervous system, and skin cells. Human victims have been known to go into shock or die of heart failure before reaching shore. Survivors however, experience considerable pain for weeks and have a significant scarring where it made contact. It is the most toxic animal on earth.
They are also called sea wasps and marine stingers they live primarily in coastal waters off Northern Australia and throughout the Indo-Pacific. They get their name from the cube-like shape of their bell.
Up to 15 tentacles grow from each corner of the bell and can reach 10 feet in length. Each tentacle has about 5,000 stinging cells, which are triggered by the presence of a chemical on the outer layer of its prey. They are considered highly advanced among jellyfish for they have developed the ability to move rather than just drift They also have eyes grouped in clusters of six on the four sides of their bell. Each cluster includes a pair of eyes with a sophisticated lens, retina, iris and cornea, although scientists aren’t sure how they process what they see since they don't have a central nervous system.
Facts:
-There are 29 different species of box jellyfish
The most well known are the big box jellyfish (most deadly) and the irukanji jellyfish and then there are 27 other lesser well known species.
-Jellyfish shrink if they don’t eat
-Jellyfish live for about three months
In the open ocean, jellyfish only live for a period of about three months but they can sometimes live for up to seven to eight months in a science lab tank.
Sources: https://www.nationalgeographic.com/animals/invertebrates/group/box-jellyfish/
http://travelnq.com/australian-box-jellyfish/