Moon jellies are free-floating, and digest whatever plankton they happen to bump into as they drift through the current. The plankton becomes covered in slime, and slides down the bell-shaped body of the jellyfish, towards the trailing oral arms. Go to Wikipedia for pictures of a moon jelly capturing prey.Fertilized moon jelly larvae form stationary polyps before dividing asexually into free-floating juvenile jellies. Check out this page to see pictures of moon jelly polyps and to learn more about how the jellies develop. If you're really intrigued by Cnidarians, check out this Seattle Times article about jellyfish, and this BBC article about killer jellyfish destroying an Irish salmon farm.