Jellyfish swim by opening its body to look like an umbrella. Then, it pushes its body together to push out water to swim and propel itself forward. A jellyfish’s mouth hangs down from the middle of its body. From that mouth it eats plankton which are very tiny, floating sea animals. An example of plankton is brine shrimp. Some jellyfish, which are large, will eat fish eggs, but other jellyfish that are larger will eat sea snails and crabs. The largest of largest jellyfish will eat small fish. Their tentacles can irritate a person’s skin but some aren't harmful. It most likely won't kill you because they don’t have enough venom in their tentacles. However some jellyfish have venom deadly enough to kill a person in 3 minutes. Jellyfish can live up to about a year. Jellyfish can be eaten. Some jellyfish can be as small as a pea and some can be about 7 feet (2 meters) long! They probably glow so they can see because they live at the bottom of the ocean ( it is very dark there). A jellyfish's predators are fish and turtles.
https://www.youtube.com/watch?v=Pu_ijC8HFRU
https://www.youtube.com/watch?v=Pu_ijC8HFRU