"Sharks are fish that have skeletons made of cartilage instead of bone. This makes them faster and lighter than other kinds of fish. We often think of sharks as being very big, but they come in all different sizes. The smallest is about the size of a cigar! There are about 500 species, or kinds, of sharks in the world. They have the same five senses humans do, plus two extra. They have special organs in their body that help them sense electrical currents and pressure changes in the water"--