Zooplankton live in many of the bodies of water around the world, from lakes to open oceans. Most exist in the upper part of the oceans where their food source, the phytoplankton, live. Zooplankton are the primary consumers of the oceans.
Other zooplankton and larger ocean animals such as fish and whales feed on zooplankton. According to the Woods Hole Oceanographic Institution, zooplankton consist of tiny organisms such as single-celled protozoans that drift among the ocean currents or swim slowly and weakly. The zooplankton also include the larvae or immature forms of larger animals, such as jellyfish or squid.
Although zooplankton rely heavily on ocean currents for transport, many of them can move on their own. Radiolarians move like amoeba by extending pseudopodia. Forams also move via pseudopodia, but these false feet have to extend through openings in the forams' shells.