"The jellyfish’s tentacles look just like cooked noodles. The tentacles hang from underneath the jellyfish’s body. They can be as long as 1 cm to 120 feet long. That is longer than a basketball court!"
Jellyfish can be as small as a grape or as big as a bed. It depends on what kind of jellyfish it is. If it is a box jellyfish and it is full grown it will be 4 meters long. If it is an umbrella jellyfish and it is full grown then it will only be about 1 inch long.
When jellyfish get washed up to shore they can’t get back in the water. If you spot one laying on the beach remember where you saw it. Go back the next day. Then you will find that the jellyfish has melted. When jellyfish melt, all there will be is some of its skin surrounding the jellyfish. The inside will have evaporated."
New England Aquarium, Boston, MA