According to the National Oceanic and Atmospheric Association (NOAA), sharks are classified as fish. Because sharks live their lives in water and make use of gills to filter oxygen from the water to breathe and survive, they fall under the fish category.
Sharks are further classified under the elasmobrachii class under the World Register of Marine Species classification guidelines because they have skeletons made from cartilage instead of bone. Other elasmobrachii in the class include rays and skates. There are more than 1,000 species included in the Class Elasmobrachii, including the shortfin mako shark, basking shark, whale shark, sawfish and southern stingray.