A jelly has no head, brain, heart, eyes, nor ears. It has no bones, either.

Where there's water—from icy polar seas to tropical Pacific shores—there are jellies. Scientists estimate there may be 2,000 species of jellyfish.

All jellies sting, but not all jellies have poison that hurts humans. Of the 2,000 species of jellyfish, only about 70 seriously harm or occasionally kill people.

Jellyfish has been around for more than 650 million years which means that they outdate the dinosaurs and the sharks.

The worlds largest known jellyfish can reach a diameter of 2.5 m/ 8ft and their tentacles can grow to be half the length of a football field.

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