It's hard to argue that sharks are one of the more fascinating creatures that live in the ocean. But are they fish? It's a common question asked by people of all ages.

Like fish, sharks have gills. Gills are used to filter oxygen from the water. But unlike fish, sharks are not made up of bones. Instead, their skeletons are made up of cartilage, which is the same gristly material that your ears and the tip of your nose is made up of.

Even though sharks are a type of fish, they do not have scaly skin like most fish. Their skin has a texture that feels exactly like sandpaper. This is because their skin is made up of tiny teeth-like structures called placoid scales. This type of skin helps sharks swim through water quickly and easily. Some sharks can even swim over 30 miles per hour!

Did you know that most sharks will die if they stop moving? In order to take in oxygen from the water, sharks must always keep water flowing over their gills. Because they have to keep moving, there are many species of sharks that never sleep. No wonder they're so grouchy!

Of all the truths about sharks, one of the most interesting might be that they have been on Earth for over 400 million years! Scientist have agreed, through the study of fossils, that sharks existed even before the dinosaurs.

Because of their fierce nature, sharks will probably always be studied very closely by humans. Like most animals on Earth, there is still a lot to be discovered.