There is only one great ocean that covers the Earth's surface. However, for the ease of location the great ocean is divided into four divisions:
The Pacific Ocean and the Atlantic Ocean are so vast that they can be divided into north and south parts with the equator being the dividing line.
The water that surrounds the antarctic continent on all sides is sometimes called the Antarctic Ocean. However, the so called Antarctic Ocean is really the southern parts of the Atlantic, Pacific and Indian Oceans.
Here are the oceans listed in order of size:
Pacific Ocean: 64 million sq. mi.
Atlantic Ocean: 33 million sq. mi.
Indian Ocean: 28 million sq. mi.
Arctic Ocean: 5 million sq. mi.
How deep are the deepest parts of the oceans? In some places you would have to dive down 7 miles to touch the bottom. (A mile is 5,280 feet.)
Mariana Trench 35,280'
Puerto Rico Trench 28,232'
Java Trench 23,376'
Eurasia Basin 17,781'
The land masses of the earth have thousands of indentations along their coasts. Ocean water fills the indentations. The indentations are given names such as gulf and bay; for example, the Bay of Biscay.
The oceans have smaller parts called seas. Generally, a sea has land on two or three sides. There are some bodies of water, not very many, that are called seas and are surrounded by land; for example, The Caspian Sea.
Finally, within the Earth's bodies of water there are channels and straits. Channels and straits serve as passageways between two pieces of land. Even a small lake may have such water passageways.