Water is essential to life and appears in different forms across the globe: fresh or salty, partly or completely surrounded by land, long and narrow or wide and round. Understanding the sometimes subtle and sometimes great differences between the different types of bodies of water can help you to grasp how they all work and help to provide for life as we know it on planet Earth.

Oceans, the largest bodies of water, cover more than two-thirds of the Earth's surface. An ocean is a vast body of salt water that surrounds a continent.

A sea is also a body of salt water, partly or completely surrounded by land, and often connected to the ocean. Seas are generally smaller than oceans.

A river is a large, flowing body of water that empties into a sea or an ocean. Streams, creeks, and brooks are smaller tributaries of a river.

A lake is a large body of water that is surrounded on all sides by land. Lakes are generally larger and deeper than ponds.

A pond is also surrounded on all sides by land and is typically smaller than a lake. Many lakes and ponds are human-made.

A lagoon is a shallow body of salt or brackish water along a coastal area. It is usually separated from the deeper sea by a shallow or exposed barrier beach area.

A cove is a small circular or oval inlet along a coastal area, often with a protected entrance. The water is partly enclosed by land formed by soft rock.

A fjord is a sea inlet characterized by long, narrow cliffs bordering it on either side.

A channel is a body of water that connects two larger bodies of water and is often used for transportation and navigational purposes.

A bay is a body of water partly enclosed by land and typically smaller than a gulf. Bays generally have calmer waters than the surrounding sea areas because they are protected by the land.