About the Picture Slideshow/Slide Show: The body of an adult jellyfish is composed of a bell-shaped, jellylike . substance enclosing its internal structure, from which the creature's tentacles suspend. Jellyfish have an incomplete digestive system, meaning that the same orifice is used for both food intake and waste expulsion.In its adult form, it is composed of 94-98% water and can be found in every pelagic area of the world. Their shape is not hydrodynamic, which makes them slow swimmers. Most jellyfish pass through two different body forms during their life cycle.
Although most jellyfish are not perniciously dangerous to humans, a few are highly toxic, such as Cyanea capillata. The recently discovered Carukia barnesi is also suspected of causing two deaths in Australia. A group of jellyfish is often called a "smack." Many species of jellyfish are also capable of congregating into large swarms or "blooms" consisting of hundreds or even thousands of individuals. Jellyfish are commonly displayed in aquaria across the United States and in other countries; among the more known are the Monterey Bay Aquarium, Vancouver Aquarium, and Maui Ocean Center.