The shark's skin isn't covered with scales, like other fish: instead the skins covered with barbs, giving it a rough texture like sandpaper.
As you know, sharks are very quick swimmers. This is made possible by their fins, one set at the side and another set underneath the body, and the tail also helps the shark move forward quickly. Unlike other fish, sharks have to keep swimming if they want to stay at a particular depth, and they rarely swim at the surface. While most other animals, including fish, hunt their prey by means of their eyesight, sharks hunt essentially by smell. They have a very acute sense of smell - and can sense the presence of food long before they can see it.