The density of a material is given in units of mass per unit volume and expressed in kilograms per cubic metre in the SI system of units. In oceanography the density of seawater has been expressed historically in grams per cubic centimetre. The density of seawater is a function of temperature, salinity, and pressure.
Explanation:
Water pressures in the deep is one of the many phenomena researchers must content with when exploring deep-sea sites. The ocean is deep. If we shaved off all the continents and filled the trenches in the oceans with the earth from the continents, the entire globe would be covered with water about 2 miles in depth. The average ocean depth is 12,566 feet about 3800 meters. The greatest ocean depth is 36,200 feet over 11,000 meters! What effect does this great depth of water have on things living in the ocean? The answer depends upon where in the ocean it lives. A fish or a plant near the surface feels little effect from the great depths. It matters little if there is six feet or six thousand feet beneath a swimming fish. An animal living at 10,000 feet depth, however, is greatly influenced by the depth of the water over it.
We often speak of pressure in terms of atmospheres. One atmosphere is equal to the weight of the earth's atmosphere at sea level, about 14.6 pounds per square inch. If you are at sea level, each square inch of your surface is subjected to a force of 14.6 pounds.
The pressure increases about one atmosphere for every 10 meters of water depth. At a depth of 5,000 meters the pressure will be approximately 500 atmospheres or 500 times greater than the pressure at sea level. That's a lot of pressure.
