Along with the Whale shark and the Megamouth shark, the basking shark is one of three species of large, filter-feeding sharks. However, the basking shark is the only one that relies on the flow of water through its pharynx by swimming. The basking shark is usually seen swimming with its mouth wide open, taking in a continuous flow of water. Food is strained from the water by gill rakers in the gill slits. The basking shark's gill rakers can strain up to 2000 tons of water per hour. These sharks feed along areas that contain high densities of large zooplankton (i.e., small crustaceans, invertebrate larvae, and fish eggs and larvae). There is a theory that the basking shark feeds on the surface when plankton is common, then sheds its gill rakers and hibernates in deeper water during winter. Also, it has been suggested that the basking shark turns to benthic (near bottom) feeding when it loses its gill rakers. It is not known how often it sheds these gill rakers or how quickly they are replaced.