Salt water covers more than 70 percent of Earth’s surface. The ocean is the continuous body of seawater that surrounds the continents and is conventionally divided into the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.

Oceans regulate global climate by storing and transporting heat. They absorb large amounts of carbon dioxide and produce much of the planet’s oxygen through phytoplankton. Marine ecosystems range from sunlit surface waters to the dark abyssal plains.

Human dependence on the ocean for food, transport, and resources is immense. Overfishing, pollution, and acidification now threaten many marine systems. Understanding ocean circulation, chemistry, and biology is essential for predicting climate and managing marine resources.

• Vast continuous body of saltwater
• Covers most of Earth’s surface
• Regulates climate and supports marine life
• Divided into five principal oceans