How does a jellyfish medusa move through water?

A jellyfish medusa moves through the water using a form of jet propulsion driven by rhythmic muscular contractions of its bell-shaped body.12

The process functions as follows:
* Contraction: Musculoepithelial cells located on the underside of the bell contract, which reduces the diameter of the bell and forces a stream of water out from the opening.32
* Propulsion: This ejection of water creates a propulsive force that moves the jellyfish through the water.13
* Recovery: After the contraction, the bell returns to its original shape through the elastic recoil of the mesoglea, the gelatinous layer that makes up the bulk of the animal's body.3

These movements are performed in a regular, rhythmic cycle. Because these contractions are generally slow, the resulting locomotion is often described as somewhat jerky. This system is coordinated by a nerve net, a decentralized nervous system that allows the jellyfish to respond to environmental stimuli without a brain.3124