The Earth is approximately 70 percent water, and nearly all of it, 96 percent, is ocean water. Water used for everyday life, however, comes from the smaller freshwater pools such as rivers and lakes. There are several classifications of bodies of water, some with distinct differences and some closely related to each other.
Brooks, creeks and streams encompass the smallest bodies of water. Brooks and creeks flow above ground while streams can flow underground. Brooks and streams can flow into larger bodies of water, and brooks often flow into rivers.
A gulf is partially enclosed by parcels of land; the Gulf of Mexico is a good visual example of the definition of a gulf. A gulf is a large area into which water from the sea or ocean flows then collects. Similarly, a bay or cove shares the same exact qualities as a gulf, but is much smaller.
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A river is a large body of water that flows in one direction, and its volume can change dramatically with precipitation levels. Oftentimes a river flows into another larger body of water, such as a lake.
A lake is a large body of water that is completely surrounded by land. The water is standing or moves slowly, and mainly comes from springs and rivers, land runoff, precipitation and melting snow and ice.
Much like a lake, a sea is also a large body of water that is surrounded by land, but it also may connect to another body of water. Seawater is a mixture of 96.5 percent water and 2.5 percent salts, with small amounts of particles and gases.
The largest body of water, an ocean is thought to have no boundaries. Oceans are the most vast bodies of water on Earth, covering 70 percent of the Earth's surface. Oceans also contain seawater or, more commonly known as, saltwater.