Freshwater Jellyfish 

Craspedacusta sowerbii, is one of the only species of jellyfish that exist in freshwater. Not a true Jellyfish at all, but actually a closely related hydrozoan. These small jellies are found in lakes and streams all over the planet. It's though that they originated in the Yangtze river basin in China. In America, they are typical found for a very short period of time in Autumn.
You can purchase your own jellyfish aquarium and live jellyfish at www.jellyfishwarehouse.com