Sharks do not have specialized organs for producing sound, so any noise a shark makes is an unintended product of its daily life, such as when it swims or eats. The draughtsboard shark can inflate itself and produces a barking sound when it fills with air instead of water.
Sharks are cartilaginous fish related to skates and rays. Over 470 species of shark exist. Sharks are an ancient and extremely successful group of animals, having existed for over 400 million years. Each shark has multiple rows of replaceable teeth. Sharks live in all oceans of the world, although some species, such as the bull shark, are capable of surviving in fresh water.