Dive into our oceans to learn why we need them--and why they need us.

Our five oceans cover about 71 percent of the earth's surface and hold about 97 percent of our water. A central part of the planet's water cycle, oceans are essential to all living things. They are home to thousands of species, and they provide humans with food and medicine. Oceans are one of the world's most valuable natural resources, and we must take care of them.