The earliest known sharks date from more than 420 million years ago, and there are now over 440 species of shark known ranging in size from the small Dwarf Lantern Shark, a deep sea species of only 17 centimetres in length, to the Whale Shark which reaches approximately 12 metres!
Sharks are cartilaginous fish, which means their skeletons are made from cartilage and connective tissue and no bones, which makes them very flexible for swimming.
Sharks are found in all seas and are common down to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater, with a few exceptions.
Sharks breathe through five to seven gill slits and several sets of replaceable teeth! They might even lose up to 30,000 in their lifetime!
Sharks have a covering of dermal denticles that protects their skin from damage and parasites, and improves their fluid dynamics so the shark can move faster.
Well-known species such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead are apex predators, at the top of the underwater food chain. Their extraordinary skills as predators fascinate and frighten humans, even as their survival is under serious threat from fishing and other human activities.
Snorkelling with Sharks