Ocean is the body of saline water that occupies the large majority of earth's hydrosphere. It is divided in to five areas, namely Pacific, Atlantic, Indian, Arctic and Antarctic. The word sea is also used in place of ocean but predominantly, the seas are inland saline bodies of water. 71% of the earth is covered with this vast body of saline water.
The average depth of this massive body of water is 12430 ft and the volume of water you find there is 1.3 billion cubic kilometers. There are 230,000 species of marine life living in the ocean. Since some of the deepest areas of the ocean are not completely explored, the number of species could go up to two million in case these areas also explored properly.
The total mass of water on earth is 1.4X10²¹Kg. This is only 0.023% of the total mass of earth. Out of all the water present on earth, only 3% is fresh water. The rest is ocean. The bluish color of sea water is due to several contributory factors but the presence of dissolved organic matter and chlorophyll are the main contributors.
Travelling on the surface of oceans dates back to prehistoric times but travel under sea was only possible after the development of modern technology. The deepest spot of the ocean is found close to Marina Islands in the Pacific Ocean. It is estimated to be 10,971 meters deep.
Ocean currents are responsible for climate changes on earth. It also regulates the carbon dioxide content in the atmospheric air. Heat from the tropics to the Polar Regions is transferred through the ocean. While the cold and warm air is transferred to coastal areas from the ocean even the precipitation is brought to coastal areas from the sea.
It is believed that life in this vast body of water started 3 billion years prior to the start of life on land. Fresh water needed for this inland life is supplied through evaporation of water from the sea. The cycle continues in order to sustain life on land.
Ocean is even important for economy. Most of the transportation of goods is done by ships with the use of sea routes. There are ports all over the world to facilitate this process. Even food is supplied by sea by way of fish, crabs, shrimps and lobsters. Catching them and processing has become an important industry for some countries in the world.