There is only one ocean. It is divided into five different parts: the Pacific, Atlantic, Indian, Antarctic, and Arctic Oceans. There are also many other smaller seas, gulfs and bays which form part of them. Altogether they cover 75 percent of the earth’s surface. For centuries, people have been challenged by the mysteries that lie beneath the ocean. However, today’s scientists have overcome many of the challenges of the depth by using modern devices. They send submarines to investigate the seabed and bring samples of marine life back to the surface for further study.