Zooplankton  /ˌzoʊ.əˈplæŋktən/ are heterotrophic (sometimes detritivorous) plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon (ζῴον), meaning "animal", and planktos (πλαγκτός), meaning "wanderer" or "drifter". Individual zooplankton are usually too small to be seen with the naked eye, but some, such as jellyfish, are large.