Freshwater jellyfish can occur in virtually any type of water body if conditions allow, including lakes, ponds, fish ponds, water-filled quarries, reservoirs, and even sluggish streams and rivers. Only one species of freshwater jellyfish occurs naturally in North America, but this species is found virtually worldwide. They are typically found in late summer during August and September. Their appearance is sporadic and unpredictable. Individuals become apparent as they rise to the water surface in afternoon to early evening, especially on clear and warm days in calm water.
Many questions remain concerning the distribution and biology of freshwater jellyfish.
Lake residents occasionally find blobs of jelly-like material attached to their dock, reeled in on a hook or washed up on shore in the summer. The strange slimy mass, that may range from clear to green or yellow to dark brown is actually a harmless colony of algae and bacteria called a bryozoan. The mass may attain the size of a basketball. The colony will not sting. Bryozoans are found in ponds, lakes and slow streams and attach themselves to vegetation or the undersides of logs and docks to avoid strong sunlight.