The circular transparent body of the jellyfish is its bell. There are four horseshoe-shaped gonads visible from the top of the bell. The disk can be 15 to 16 inches in diameter. They do not have a brain. There are networks of neurons which work automatically like a robot. About 95% of their body is nothing but water.
Moon jellies cannot move. They just drifted with the water currents. The currents tent to gather thousands of them near the coastal areas. Such gathering is known as a bloom.
They are carnivores. Small invertebrates are their principle prey. When these small sea creatures come near them they use the sting to make them motionless. So, the sting is their attack as well as defense weapon.
They have many enemies. Ocean Sunfish or Mola mola loves to eat them. There are also Leatherback sea turtles. Some birds also attack their bell to eat small insects getting a free ride on top. To defend themselves from theses enemies, the moon jellies often uses their venomous stings