Because of it's unique hydrological and hydrobiological characteristics the Black sea is one of the most interesting and researched seas. It is at about four times bigger than Bulgaria and represents 1/853 part from the World Ocean. The deepest point of the sea is 2245m, the average depth - 1271m. Black sea is typical inner sea. The full length of it's coastline is 4090km. It is connected with the Murmur sea by the Bosphor, which is deep 50m, and further with the Mediterranean sea by the Dardanels. The Black sea basin had sustained many methamorphoses with the time, the connection to the other basins had influenced the geomorphology of the constant shoreline, the relief, the bottom and the water exchange.

 
     The typical Black sea climate has a mild winter and comparatively warm summer wit many sunny days. The athmospheric motion has an important effect upon the forming of the climate over the water surface. The Black sea is almost twice less salty than the other seas. This is due to the sea's hydrological specifics, the way of forming of it's water amount, it's structure and dynamics. The high and low tides are insignificant, so they can be ascertained only if using appropriate equipment. As a result of the specific vertical disposal of the temperature and saltness a two distinct strata had formed. The upper one, from the surface up to the 200 m dept, contains oxygen, but in the lower one the oxygen is replaced with hydrogen sulphide. There is no other sea on the planet Earth with the same kind of underwater strata.

     Because of it's uniqueness and mystery Black sea has a remarkable place in the annual report of National Geographic Association. The world renowned discoverer of the shipwrecks of Titanic, Yorktown and Lusitania, had initiated the first Bulgarian - American expedition "Noi - 2001". Dr. Balard's team was looking for evidence, proving the hypothesis, that there had been a deluge in the Basin of the Black sea and that people had lived on the bottom on the sea some 8 000 years ago.
http://www.nationalgeographic.com/blacksea/ax/