Plankton are tiny plants and animals that float or drift in water. Phytoplankton are plant plankton that photosynthesize to produce their own food and provide the base of the ocean food chain by being eaten by zooplankton. Zooplankton are animal plankton that feed on phytoplankton and each other, and are in turn eaten by larger animals like fish. Together, plankton, zooplankton, and larger animals form complex food webs that sustain ocean life.