Most sharks do not eat plankton. Planktonic organisms are generally too small and lack the caloric density that most sharks require, which hunt larger, more energy-rich prey.
However, a few species have evolved to feed on plankton. Basking sharks and whale sharks are filter-feeders that swim with their mouths open, straining enormous volumes of water to capture plankton. These specialized adaptations allow them to survive on a diet of tiny organisms.