Only 30% of Earth’s surface is exposed land. the rest is covered by a huge body of salt water with a volume of more than 1 billion cubic kilometers: the world ocean. Twice a day, the oceans of the globe rise and fall by several meters. Tides are caused by the gravitational pull of the Moon , and to a certain extent of the Sun , on our planet. the seas and oceans also move in waves —undulations of the surface of the water generated by the wind. Ocean currents , on the other hand, are movements of huge masses of ocean water along very precise routes.

The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth and contains 97% of Earth’s water. Another definition is “any of the large bodies of water into which the great ocean is divided”. Historically, there are four named oceans: the Atlantic, Pacific, Indian, and Arctic. However, most countries – including the United States – now recognize the Southern (Antarctic) as the fifth ocean. The Pacific, Atlantic, and Indian are the most commonly known. More modernly, the seven seas have been used to describe regions of the five oceans—the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian, and Southern Oceans.

The Arctic Ocean is the smallest of the world’s five ocean basins. A polar bear walks on the frozen surface of the Arctic Ocean. The freezing environment provides a home for a diverse range of creatures. With an area of about 6.1 million square miles , the Arctic Ocean is about 1.5 times as big as the United States.

Of the five ocean basins, the Atlantic Ocean is the saltiest. On average, there is a distinct decrease of salinity near the equator and at both poles, although for different reasons. Near the equator, the tropics receive the most rain on a consistent basis.

The hottest ocean area is in the Persian Gulf, where water temperatures at the surface exceed 90 degrees Fahrenheit in the summer. Another hot area exists in the Red Sea, where a temperature of 132.8 degrees Fahrenheit has been recorded at a depth of about 6,500 feet.

Some of the clearest, bluest ocean waters on Earth are found in the South Pacific.

Vast stretches of salt water
the world ocean is divided by the continents into four main regions ( Pacific , Atlantic , Indian , and Arctic ) and many smaller basins, the seas, most of which are shallow and set back from the oceans. While marginal seas, such as the South China Sea, open out to an ocean, enclosed seas, such as the Mediterranean, are attached to an ocean by a narrow passage. Some salt lakes that have no contact with the ocean are also called seas; an example is the Caspian Sea.

Arabian Sea, 3,600,000 km2 Yemen, Oman, Iran, Pakistan, Somalia
South China Sea, 3,500,000 km2 China, Taiwan, Philippines, Malaysia, Vietnam
Weddell Sea, 2,800,000 km2 Antarctica
Caribbean Sea, 2,600,000 km2 Venezuela, Colombia, Central American countries, Antilles
Mediterranean Sea, 2,510,000 km2 France, Italy, Greece, Turkey, Egypt, Libya, Tunisia, Algeria,
Morocco, Spain
Bay of Bengal, 2,170,000 km2 Sri Lanka, India, Bangladesh, Myanmar
Gulf of Mexico, 1,540,000 km2 Mexico, Cuba, United States
Barents Sea, 1,405,000 km2 Norway, Russia
Sea of Japan, 970,000 km2 Japan, South Korea, North Korea, Russia
East China Sea, 770,000 km2 China, North Korea, South Korea, Japan, Taiwan
North Sea, 570,000 km2 Norway, Denmark, the Netherlands, France, United Kingdom
Red Sea, 450,000 km2 Saudi Arabia, Yemen, Erytrea, Sudan, Egypt
Beaufort Sea, 450,000 km2 Canada, United States
Black Sea, 420,000 km2 Ukraine, Russia, Georgia, Turkey, Bulgaria, Rumania
Persian Gulf, 233,000 km2 Iraq, Iran, United Arab Emirates, Saudi Arabia, Kuwait

Pacific, 165,000,000 km2, 707,000,000 km3, 135,663 km, 11,034 m (Mariana Trench)
Atlantic, 82,400,000 km2, 323,600,000 km3, 111,866 km, 8,605 m (Puerto Rico Trench)
Indian, 73,400,000 km2, 292,000,000 km3, 66,526 km, 7,125 m (Java Trench)
Arctic, 14,000,000 km2, 16,700,000 km3, 45,389 km, 5,669 m (Molloy Hole)