Sharks Introduction. Sharks have lived in the oceans since before dinosaurs walked on Earth. Hundreds of kinds of sharks can be found all over the world. Sharks are fish, but their skeletons are made of cartilage instead of bones. Cartilage is what gives human ears their shape. Unlike most fish, sharks have rough skin. Sharks have a good sense of smell. They also see well in the dark. Sharks can sense other animals moving in the water. Description. Great white shark come in many sizes. Some sharks are only a few inches long. The huge whale shark is the largest fish in the world. Many sharks are dark on the top and light on the bottom. This shading makes it harder for other animals to see them. Sharks swim by swinging their tails from side to side. Fins help sharks steer, turn, and keep their balance. Eating. Most sharks have many rows of teeth. When one tooth breaks off, another one moves up to take its place. Most sharks eat fish. Large sharks eat sea lions, dolphins, and other sharks. Some sharks eat shellfish. These sharks have flat teeth for crushing shells. The huge whale shark has tiny teeth but doesn't use them when eating. It swallows very small ocean plants and animals that float near the ocean's surface. Shark Attacks. Many people are afraid of sharks, but most sharks do not attack humans. Great white sharks are one of the few kinds of sharks that are dangerous to people. Shark Hunting. Shark fishing boats. People hunt sharks for their skin, oil, and teeth. Many people eat shark meat, and shark fins are used to make soup. Many kinds of sharks are now in danger of being completely killed off. Sharks are an important part of the balance of life in the world's oceans. They have as much right to live as any other animal.