VIDEO: Cassiopea Jellyfish (video) California Institute of Technology Share Print E-Mail Loading video... Caption The jellyfish Cassiopea spends most of its life resting on underwater surfaces, pulsating gently. Caltech scientists have now discovered that these jellyfish actually exhibit a surprising behavior: sleep. Credit Caltech Usage Restrictions with proper credit Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.