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Seawater

Water that is found in the oceans is known as seawater. Seawater has approximately 35g of dissolved salt in every liter of water (or 3.5% salinity). Most of this salt consists of sodium chloride. The density of seawater is about 1.025g/ml compared to fresh water density of 1.000g/ml. The presence of dissolved salt in seawater will reduce its freezing point to -2 °C.

In fact, salinity of seawater is normally between 3.1% and 3.8%. The level of salinity will not be constant in the oceans all over our planet. At places where fresh water from rivers enter the oceans and in places where ice glaciers are melting, the level of salinity of seawater will be lower because seawater is mixed with fresh water.

In places like the Red Sea where the rate of water evaporation is very high but the amount of rainfall is very low, the level of salinity in seawater is unusually higher. The Red Sea has a density between 1.028 and 1.035g/ml. It is an isolated body of salt water. It has a salinity of 33.7% and a density of 1.24g/ml.