Water occupies 71% of its surface. The ocean was formed around 4,000 million years ago. Then, when the tectonic plates separated, they divided the five big oceans that we currently know: The Pacific, the Atlantic, the Indian, the glacial Arctic and the glacial Antarctic
The oceans along with rivers and lakes form the hydrosphere; that is to say, the global set of waters of the planet earth. The oceans contain 96% of liquid water in the Earth. It means that just 4% is fresh water. The salinity of water comes from three sources: salt and potassium that rain washes from terrestrial rocks, the sea water filtration through the cracks of hydrothermal vents in the seabed that comes back loaded with salt and the eruptions of submarine volcanoes.