he sea enters the composition of the ocean. This large body of water can be clearly separated from other waters with coastal strips or islands. The sea has quite limited possibilities of water exchange, and therefore has different rules for this phenomenon, called the hydrologic regime.

All seas constitute 11 percent of all water in the world, the total area is approximately 40 million of km ². There are 71 seas, without the Caspian Sea and the Dead Sea, which despite the name, however, are salt lakes.

There are many classifications of the seas. One of them divide them in coastal, which are the ones that are separated from the ocean with only a string of islands, and this allows a simple exchange of water. On the other hand, the mediterranean seas, which are located between the land are much cut off from the ocean and the water exchange is done only through a narrow strait.

A detailed breakdown of the seas is done in terms of more characteristics. In this case, you can point out open sea. This category includes, among others Arabian Sea, Norwegian Sea, North Sea, which have a very extensive connection with the ocean. Another type is a coastal sea (the Kara Sea, Sea of ​​Japan, South China Sea), which are separated from the ocean with islands or peninsulas. Then there are the interisland seas found only among the islands or archipelago. This is the case of the Irish Sea, Celebes Sea and the Java Sea. Sea located between the continents, is defined as intercontinental, such as the Mediterranean Sea, Red Sea, Caribbean Sea. The last type is intracontinental sea, that is, sea inside the continent (the Baltic Sea, White Sea, Sea of Azov).

The only exception to this typology is the Sargasso Sea, which is a part of the open waters of the Atlantic, without any particular limit. However, the water in this tank clearly indicate a distinct climatic and biological properties.