The average depth of the sea ranges from a few meters to two or three kilometers, and the average depth of the ocean is about 3795 meters. The sea is close to the mainland and is influenced by the mainland, rivers, climate and seasons. The temperature, salinity, color and transparency of seawater are all influenced by the land and have obvious changes. Ocean is the central part of the ocean and the main body of the ocean. The total area of the world's oceans accounts for about 89% of the ocean area.

The water depth of the ocean is generally more than 3000 meters, and the deepest point can reach 1 10,000 meters. The ocean is far from the land and is not affected by the land. Its moisture and salinity have little change, and each ocean has its own unique ocean current and tidal system. The water in the ocean is blue and transparent, and there are few impurities in the water.

Extended data

Seawater temperature: Seawater temperature is a physical quantity reflecting the hot and cold state of seawater. The water temperature of the world's oceans generally varies between-2℃ and 30℃, and the area where the annual average water temperature exceeds 20℃ accounts for more than half of the whole ocean area. The sea water temperature varies periodically and irregularly in days, months, years and years, which mainly depends on the ocean heat budget and its time variation.

Generally speaking, the factors affecting the surface water temperature of the ocean are tides, solar radiation, coastal topography, meteorology, ocean currents and so on. The direct observation shows that the daily variation of seawater temperature is very small, and the water depth varies from 0 to 30 meters, while the annual variation can reach the water depth of about 350 meters.

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