Sharks are the most feared creatures under the sea -mostly due to movies like Jaws . On average there is one Australian killed by a shark each year. Sharks come in all sizes, shapes, and colors. The most popular sharks are the great whites or tiger sharks.
Sharks are the only fish that have cartilage instead of bones.
Cartilage is more flexible, therefore, sharks can turn sharper corners than other fish. Cartilage is continually being replaced and mineral deposits are in their jaws which results in stronger teeth. Shark's teeth are normally replaced every eight days. An average shark goes through 30,000 teeth in their lifetime. Sharks don't have overlapping scales like fish do, but have really rough skin.