A famous French oceanographer, J. Cousteau, gives the following account as a result of his studies in water barriers: “We studied the assertions by certain researchers about barriers separating seas, and noticed that the Mediterranean Sea had its own salinity and density and housed autochthonous fauna and flora.

The construction of submarines dates back to the 17th century. A vessel that navigated under water was first contrived in 1620 by C. Drebber. Submarines developed rapidly, and in 1954, nuclear submarines were made.