Explore sharks--the ocean's most fearsome and fascinating fish alive! Did you know that there are more than 400 species of shark? Or that a great white shark can go through 20,000 teeth in a lifetime? Discover more about how sharks have existed in the oceans for more than 400 million years--that's older than the dinosaurs! Ignite your scientific mind with fun facts, activities, and experiments. Try this: With clean hands, feel...