Its lengthy tentacles have tens of thousands of microscopic nematocysts, which secrete toxins when stimulated.
While barely bigger than a golf ball, its poison is deadly enough to put an adult human to sleep in minutes.
They have venomous spines on their backs that can cause unbearable agony, paralysis, and even death.
These monsters, which can reach six meters, are responsible for more human deaths in Australia than any other species.