1. They are not actually fish! Jellyfish are invertebrates, meaning they have no backbone. Because they aren't fish at all, many scientists prefer to call them sea jellies.

2. They have no brains, hearts, or bones. Jellyfish are about 95% water! Instead of a brain, they rely on a simple network of nerves (called a "nerve net") to sense light, odor, and movement around them.

3. They existed before the dinosaurs. Jellyfish have been swimming in the world's oceans for over 500 million years, making them older than dinosaurs, trees, and sharks!

4. Some can glow in the dark. Many species of jellyfish have bioluminescence, which means they produce their own light. They use glowing colors like blue and green to confuse predators or attract prey in the deep ocean.

5. Their tentacles shoot microscopic poison darts. Jellyfish tentacles are covered in thousands of tiny stinging cells called nematocysts. When touched, these cells spring open like tiny harpoons to catch food.

6.A group of jellyfish is called a bloom, swarm, or smack. While a group of fish is called a school, hundreds or thousands of jellyfish swimming together form a massive "smack"!

7. They move by jet propulsion. Jellyfish swim by squeezing their umbrella-shaped bodies to squirt out water behind them, pushing themselves forward just like a tiny rocket underwater!