Turkey is surrounded by sea on three sides, by the Black Sea in the north, the Mediterranean in the south and the Aegean Sea in the west. In the northwest there is also an important internal sea, the Sea of Marmara, between the straits of the Dardanelles and the Bosphorus, important waterways that connect the Black Sea with the rest of the world. Because the mountains in the Black Sea region run parallel to the coastline, the coasts are fairly smooth, without many indentations or projections.

The length of the Black Sea coastline in Turkey is 1,595 kilometers, and the salinity of the sea is 17 percent. The Mediterranean coastline runs for 1,577 kilometers and here too the mountain ranges are parallel to the coastline. The salinity level of the Mediterranean is about double that of the Black Sea.

Although the Aegean coastline is a continuation of the Mediterranean coast, it is quite irregular because the mountains in the area fall perpendicularly into the Aegean Sea coast is over 2,800 kilometers. The coastline faces out to many islands. The Marmara Sea is located totally within national boundaries and occupies an area of 11,350 square kilometers. The coastline of the Marmara Sea is over 1,000 kilometers long; it is connected to the Black Sea by the Bosphorus and with the Aegean by the Dardanelles.