Whale sharks get their name from their massive size—they can grow to be as large as whales and are the biggest fish in the ocean. These sharks can reach lengths of 40 feet—about the length of a school bus—and can weigh more than 20 tons.

Whale sharks have multiple rows of teeth, but they’re not the triangular, jagged teeth associated with most sharks. Their 3,000 teeth are no larger than a pinhead. Because their teeth are so small, whale sharks only eat small organisms such as plankton, krill and small fish. They consume their meals by filtering water through their large mouths as they swim.

Each whale shark also has a unique pattern of white spots. Like human fingerprints, these distinct patterns help researchers identify and track individual whale sharks to provide information on how they grow and how long they can live. Monitoring whale sharks by their unique spots also helps researchers determine how many whale sharks—which are listed as endangered by the International Union for the Conservation of Nature (IUCN)—are left in the ocean. 

Read more about whale sharks and their endangered status here.