With their many different species, jellyfish are found in every ocean in the world, including very cold waters of the Arctic and Antarctic. Some are even found in freshwater. Some species live in shallow, sunlit waters near the surface, while others live in the deep, dark, cold or somewhere in-between. Here are a few other points.

1. They predate dinosaurs, bobbing along in the currents for at least 500 million years and possibly 700 million years, roughly three times the age of the first dinosaurs.
2. They aren’t fish. They don’t have a backbone or spine, nor do they have brains, hearts, eyes, scales, gills, or fins. Instead, they swim by opening and closing their “bells.” Many scientists simply group them as “gelatinous zooplankton.”
3. A few species have surprisingly complex vision. For instance, the box jellyfish has 24 “eyes,” two of which can see in color. It’s also believed this animal’s complicated array of visual sensors makes it one of the few creatures to have a full 360-degree view of its environment.
4. Its lifespan depends on the species in question. Some live for just a few days or weeks, while others can live for several decades or more. One species, called the immortal jellyfish (Turritopsis dohrnii), is capable of reversing its life cycle and returning to a younger stage of development after it reaches sexual maturity. This means that it can essentially live forever as long as it is not killed by predators or other external factors.
5. This ability is a major subject of research, as it could help the medical field understand how to turn cancerous cells into noncancerous cells like muscles, nerves, or skin.
6. Jellyfish use tentacles to catch their food. These long, thin appendages on the sides and bottom of the jellyfish’s body are covered in tiny stinging cells that contain a venom to stun and capture prey. When they encounter something edible, they use their tentacles to bring it closer to their mouth, located in the center of their body.
7. They are carnivores, meaning they eat other animals. Since they’re unable to chew their food, they usually eat small marine animals they can swallow whole, such as
8. plankton, small fish, and crustaceans like shrimp and lobsters. They’ll also eat smaller jellyfish.
9. The power of their stings can vary widely depending on the species. The most venomous is probably the box jellyfish, capable of killing an adult human in just a few minutes with a single sting. Each box jellyfish reportedly carries enough venom to kill more than 60 humans. To make matters worse, their stings are excruciatingly painful — it’s said the pain could kill you before the venom does.
10. Jellyfish are eaten by larger predators, such as tuna, sea turtles, and whales. They’re even a delicacy in some places, such as in Japan and Korea. The Japanese have transformed jellyfish into candy. More often, they find their way into salads, fried into crunchy noodles, or are eaten with soy sauce like sushi.