"Aurelia aurita (also called the moon jelly, moon jellyfish, common jellyfish, or saucer jelly) is a widely studied species of the genus Aurelia. All species in the genus are closely related, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus.
The medusa is translucent, usually about 25–40 cm in diameter, and can be recognized by its four horseshoe-shaped gonads, easily seen through the top of the bell. It feeds by collecting medusae, plankton and mollusks with its tentacles, and bringing them into its body for digestion. It is capable of only limited motion, and drifts with the current, even when swimming." - http://en.wikipedia.org/wiki/Aurelia_aurita
I actually really like how this turned out. ^^ I hope it looks like a moon jellyfish. I was drawn at 3:58 AM so it probably doesn't look very accurate. ;^^