Marine biology is the scientific study of organisms in the ocean or other ocean or salt water bodies. In view of the fact that many branches, families and genera in biology have some species living in the sea and other species living on land, marine biology classifies species according to the environment rather than taxonomy. Marine biology is different from marine ecology, because marine ecology focuses on how organisms interact, while environment and biology are the study of animals themselves.

Marine life is a huge resource, which provides food, medicine and raw materials in addition to helping to support entertainment and tourism all over the world. Fundamentally speaking, marine life helps to determine the nature of our planet. Marine life makes an important contribution to the oxygen cycle and participates in regulating the earth's climate. [1] The coastline is shaped and protected by marine life, and some marine life even helps to create new land. [2]

Marine biology covers a large number of contents, from the microscopic level, including most zooplankton and phytoplankton, to the reported giant cetaceans (whales) as long as 48 meters (125 feet).

The habitats studied in marine biology range from the tiny layer of surface water where the surface tension between the ocean and the atmosphere may trap living and non-living projects to the depth of deep-sea trenches, sometimes below the ocean surface 10000 meters or more. It studies habitats such as coral reefs, seaweed forests, tidal pools, silt, sand and rock bottoms, and open ocean (ocean) areas, where there are few solid objects and the water surface is the only visible boundary.

A large number of creatures on the earth exist in the ocean. The exact proportion is unknown, because many marine species have yet to be discovered. Although oceans account for about 7 1% of the earth's surface, because of their depth, they contain about 300 times the habitable volume of terrestrial habitats on the earth.

Many species are of great economic significance to human beings, including eating fish. People have gradually realized that the well-being of marine life and other life is linked in a very basic way. With new discoveries almost every day, human knowledge about the relationship between marine life and important cycles is growing rapidly. These cycles include material cycle (such as carbon cycle) and air cycle (such as earth's breath and energy movement through ecosystems including the ocean). Large areas under the ocean surface have not been effectively explored.