There are many different species of jellyfish and most of these, including the moon jellyfish, live in the world's oceans. Jellyfish species were not originally found all over the world's oceans, but they were moved around by accident over many years by ships.
The jellyfish is a species that has existed longer than most of the animals currently populating the Earth's land and oceans. In fact, the jellyfish was alive before the dinosaurs walked the Earth. The jellyfish are highly adaptable and though they prefer deeper water, they can also live in shallow water. They can also adapt in a variety of climates from tropical ocean temperatures to sub-polar ocean environments.