The general term for organisms that drift in the water is plankton. Plankton includes both phytoplankton (autotrophic organisms, primarily microscopic plants) and zooplankton (heterotrophic organisms like tiny animals). These organisms are crucial to aquatic ecosystems, serving as the primary producers and consumers in the marine food web. They play significant roles in nutrient cycling, energy transfer, and supporting the diverse life forms in oceans and freshwater systems.