The Black Sea is an inland sea bounded by Europe, Anatolia and the Caucasus. It is connected to the Atlantic Ocean via the Mediterranean and Aegean Seas. In the aftermath of the last ice age, water levels in the Black Sea and the Aegean Sea rose independently until they were high enough to exchange water. The Black Sea was originally a land-locked fresh water lake and was flooded with salt water during the Holocene. The influx of salt water essentially smothered the fresh water below it, which meant that no oxygen could reach the deep waters. This created a meromictic body of water. This type of underwater environment is hostile to many biological organisms that destroy wood in the oxygenated waters and provides an excellent site for deep water archaeological survey.

In a series of expeditions, a team of marine archaeologists led by Robert Ballard identified what appeared to be ancient shorelines, freshwater snail shells, and drowned river valleys in roughly 300 feet (100 m) of water off the Black Sea coast of modern Turkey. Radiocarbon dating of freshwater mollusk remains has indicated an age of about 7,500 years. The team discovered three ancient wrecks to the west of the town of Sinop at depths of 100 m. According to a report in New Scientist magazine, the archeologists uncovered an underwater delta south of the Bosporus. They discovered evidence for a strong flow of fresh water out of the Black Sea in the 8th millennium BC.

The evidence has helped support the Black Sea deluge theory. In 1997, William Ryan and Walter Pitman from Columbia University published a hypothesis which cited information on a massive flood through the Bosphorus (strait) that occurred in ancient times. They claim that the Black and Caspian Seas were vast freshwater lakes, but then about 5600 BC (7611 years ago), the Mediterranean spilled over a rocky sill at the Bosphorus, creating the current link between the Black and Mediterranean Seas. The event is said to have flooded 155,000 km2 (60,000 sq mi) of land and significantly expanded the Black Sea shoreline to the north and west. According to the researchers, "Ten cubic miles (42 km3) of water poured through each day.”

It is widely accepted by the scientific community that the floods did occur and similar events have been recorded in the post-glacial period. However, there is a debate over the suddenness and magnitude of the water shift. Publications have been made to support and to discredit the Black Sea deluge theory, and archaeologists still debate the hypothesis. The claims have led some to associate this catastrophe with prehistoric flood myths. The oscillating hypothesis specifies that over the last 30,000 years, water has intermittently flowed back and forth between the Black Sea and the Aegean Sea in relatively small magnitudes, and does not necessarily predict that any sudden "refilling” events.