An ocean is a body of saline water that composes much of a planets hydrosphere. Salinity is a main defining component of the ocean, and it is the amount of dissolved solid material in the water. Although there are many dissolved salts in seawater, sodium chloride (commonly known as salt) is the most abundant. This is what makes oceans unique to other aquatic ecosystems. The amount of salt water required to maintain and balance the ocean is greater than the amount of fresh water needed.
Oceans of the earth take up about 140 million square miles covering neatly 71% of the earth’s surface. The deepest point in the ocean is 36,198 feet! The five world oceans are the Pacific, Atlantic, Indian, Southern and Arctic Oceans. Ocean ecosystems have distinct characteristics and contain various life forms found only in this environment.