Jellyfish are simple multicellular animals with the following characteristics:

1. Soft posture: The jellyfish's posture is similar to a conical umbrella, and the whole posture is very soft.

2. High transparency: the organizational structure of jellyfish is very simple, only composed of cells, so the jellyfish body is transparent and can see the operation of internal organs.

3. Powerful biological flexibility: Jellyfish have no bones, tentacles or other parts of their feet, but they can swim at a fast speed by shrinking the body wall and turn to their own direction at will.

4. Simple digestive system: The digestive system of jellyfish is very simple, with only one mouth and one digestive bag, and its ability to digest food is not strong.

5. Unique way of breathing: jellyfish have no respiratory organs. They draw oxygen from the water by expanding and contracting the body wall.

6. Variety of reproduction methods: The reproduction methods of jellyfish are mainly divided into sexual reproduction and asexual reproduction, and some jellyfish can also divide and reproduce.

7. Terrible toxicity: Many jellyfish contain highly toxic stinging cells. Once in contact with humans, it will cause uncomfortable reactions such as skin tingling, redness and itching, and may also lead to serious consequences such as allergies and nervous system damage.