There are a hell of a lot of species of Jellyfish in the world, and the vast majority of them are pretty stingy. On a human, most of the effects will run from a mild irritation to an electric-shock-like burning pain. Unfortunately Australia has some of the worst examples of Jellyfish bastardry to be found anywhere in the world. There is also a the Portuguese Man o War included here just because it seemed logical even though it’s not technically a jellyfish.