People tend to think about sharks in one of two ways.
Either they fear sharks intensely or they are completely fearless and see them as harmless animals they can pet. Probably the most realistic view of sharks is somewhere in between. The vast majority of shark species are completely harmless to humans, but there are some that when provoked or mistake humans for prey can cause injury. Sharks, members of the phylum Chordata, have skeletons of cartilage and occur in a variety of shapes and sizes. In addition to their tough skin, all sharks are equipped with streamlined bodies, allowing them to swim effortlessly through the water.