There are over 350 species of sharks, but only 30 are dangerous to humans. The document goes on to describe 13 different shark species, including the gray reef shark, blacktip shark, sand tiger shark, shortfin mako shark, blue shark, great hammerhead shark, oceanic white tip shark, tiger shark, bull shark, and great white shark. It provides details on the appearance, habitat, behaviors and threats to some of these sharks.