They are aquatic vertebrates with gills and fins. The Whale Shark is also the largest fish in the world.
Sharks feed primarily on fishes, crabs, mollusks, seabirds and seals, etc.
There are about 50 types of sharks out of 370 that are hazardous to humans. Other species requiring caution are the Blacktip, Blacktip Reef, Gray Reef,, Galapagos, Shortfin Mako, and Great Hammerhead Sharks. Sharks weed out the infirm and keep breeding populations healthy. They help maintain the natural balance of the marine ecosystem. Sharks usually feed at night.