The box jellyfish is one of the most venomous animals on the planet-- not just in Australia, and the deadliest marine animal known to man. These powerfully venomous jellies are characterized by long, transparent tentacles that have millions of venom-carrying, harpoon like darts. Active mostly during the period from October through May (a time known as 'stinger season' in northern Australian coastal areas), the box jelly can be difficult to detect in the water due to its transparency.
The vast majority of human deaths caused by jellyfish are caused by the box jellyfish, and though fewer than 100 people have died as a result of jellyfish stings since 1883, the box jellyfish's venom quickly shuts down vital organs such as the heart and nervous system. This capacity to quickly dispatch a human victim is what makes the box jelly so deadly, and a sting from this animal can cause human death within minutes. However, certain precautions can be taken to protect oneself from a box jellyfish sting, including wearing a protective sting suit and heeding any posted warnings on beaches in affected regions.