Pontos

The Black Sea is connected to the World Ocean by a chain of two shallow straits, the Dardanelles and the Bosporus. The Dardanelles is 55 m (180 ft) deep and the Bosporus is as shallow as 36 m (118 ft). By comparison, at the height of the last ice age, sea levels were more than 100 m (330 ft) lower than they are now. There is also evidence that water levels in the Black Sea were considerably lower at some point during the post-glacial period. Some researchers theorize that the Black Sea had been a landlocked freshwater lake (at least in upper layers) during the last glaciation and for some time after. In the aftermath of the last glacial period, water levels in the Black Sea and the Aegean Sea rose independently until they were high enough to exchange water. Currently, the Black Sea water level is relatively high; thus, water is being exchanged with the Mediterranean.

The Black Sea undersea river is a current of particularly saline water flowing through the Bosporus Strait and along the seabed of the Black Sea. The discovery of the river announced on August 1, 2010, was made by scientists at the University of Leeds and is the first of its kind in the world. The undersea river stems from salty water spilling through the Bosporus Strait from the Mediterranean Sea into the Black Sea, where the water has a lower salt content.

While the net flow of water through the Bosporus and Dardanelles (known collectively as the Turkish Straits) is out of the Black Sea, generally water is flowing in both directions simultaneously. Denser, more saline water from the Aegean flows into the Black Sea underneath the less dense, fresher outflowing water from the Black Sea. This creates a significant and permanent layer of deep water that does not drain or mix and is therefore anoxic. This anoxic layer is responsible for the preservation of ancient shipwrecks which have been found in the Black Sea.

The Black Sea was a busy waterway on the crossroads of the ancient world: the Balkans to the west, the Eurasian steppes to the north, the Caucasus and Central Asia to the east, Asia Minor and Mesopotamia to the south, and Greece to the south-west. The Black Sea was sailed by Hittites, Carians, Colchians, Thracians, Greeks, Persians, Cimmerians, Scythians, Romans, Byzantines, Goths, Huns, Avars, Slavs, Varangians, Crusaders, Venetians, Genoese, Georgians, Tatars and Ottomans.

Popular supposition derives the name "Black Sea" from the dark colour of the water or climatic conditions. Some scholars understand the name to be derived from a system of colour symbolism representing the cardinal directions, with black or dark for north, red for south, white for west, and green or light blue for east. Hence "Black Sea" meant "Northern Sea".

In the Greater Bundahishn, a Middle Persian Zoroastrian scripture, the Black Sea is called Siyābun. In the tenth-century Persian geography book Hudud al-'Alam, the Black Sea is called Sea of the Georgians (daryā-yi Gurz). The Georgian Chronicles use the name zğua sperisa (ზღუა სპერისა or Sea of Speri) after the Kartvelian tribe of Speris or Saspers. During the Ottoman Empire, it was called either Bahr-e Siyah or Karadeniz, both meaning "Black Sea" in Turkish, with the former consisting of Perso-Arabic loanwords.

There have been isolated reports of flares on the Black Sea occurring during thunderstorms, possibly caused by lightning igniting combustible gas seeping up from the sea depths.

In Ukraine there is one tale that has been passed down for generations, explaining the sudden bursts of turbulence and violent waters. The legend tells of a sensible man named Bogatyr, who was known for his courage and strength, and who had a magical arm. It is said that his arm was a mythical arrow, but for all the power it wielded, it was destructive and harmful. If the power of this arm was given to the wrong person, it would cause wars and despair. The arrow could boil water, melt the earth, set the air on fire and kill. When Bogatyr sensed that his time on earth was nearing its end, he began to worry about the future of the arrow, and that the next person who possessed it might not be as sensible with it as he was. So he decided to hide it.

Even though his sons were great warriors and honest people, Bogatyr feared that their young age and the extreme power of the arrow would make them unable to resist the temptation, so he enlisted them instead to help him hide the arrow. They were instructed to take the arrow, and toss it deep into the Black Sea, where future generations would not be able to find it. On arriving at the Black Sea, they decided to rather hide the arrow in the mountains and tell their father that they had fulfilled his wish. Bogatyr already knew their plans and sent them back to complete their task under the threat that they would not receive his blessings until the arrow was lying at the bottom of the Black Sea. The sons complied, and legend has it that as soon as the arrow touched its waters, it turned black and began to boil. It is believed that the sea cannot rest and that the waves and boiling water that occur at times are the Black Sea trying to rid itself of the fiery arrow.

According to the ancient Greek legends, the princess Io, beloved by the main Olympic god Zeus, was turned into a cow by the goddess Hera and wandered in the search of refuge on the territory of the modern Republic of Crimea. Pursued by a huge gadfly sent by Hera, the desperate Io swam across the modern Kerch Strait, entrance to the Black Sea, which the Hellenes began to call the Cimmerian Bosphorus, or “cow ford”.

The principal Greek name of the Black Sea was "Πόντος Ἄξεινος/Póntos Áxeinos", meaning "Inhospitable Sea", and is generally accepted to be a rendering of Iranian word *axšaina- (dark coloured). Accordingly, myth developed to explain the name. The Black Sea was rich in fish, and the coastal lands were rich in construction timber and iron, but sailing in the Black sea was dangerous for seamen. The weak indentation of the coasts meant there were few convenient places for the harbours, and there were almost no islands and peninsulas, and for a long time the coastal areas of the Black Sea remained unexplored. Travellers' stories gave rise to the legends about the Inhospitable Sea which smashed and drowned ships, about huge eagles and gryphons that attacked the Hellenes from the air, and about the treacherous mountaineers who were waiting for galleys of men to sacrifice on the altar of a bloodthirsty goddess. The ancient historian Diodorus of Sicily narrates that in those days the coastal nation of Taurida was ruled by the insidious goddess of witchcraft and darkness, Hekate, who had poisoned her father Perses, the son of the sun god Helios, to obtain power. It was she who had erected the sanctuary on the rocky shore of the sea, in which they sacrificed all the strangers sailing to her country. The ancients also called her the mother of two great sorceresses, Kirk (Circe) and Medea, who became the heroines of certain myths.

The period of the great Greek colonization contributed to the active development of the lands of Taurida and the emergence of many settlements of the ancient Hellenes. Cruises by the ships became safer, and the Black Sea was renamed “Εὔξεινος Πόντος/Eúxeinos Póntos”, or "Hospitable Sea". More simply, however, the Black Sea was often just called Pontos, or "the Sea" (ὁ πόντος ho Pontos).

In Greek mythology, Pontos was the primordial god and a personification of the sea. He was the sea itself but also its resident deity, a deathless god born from the earth at the dawn of creation. By Gaia, Pontos fathered the ancient deities known as the Old Men of the Sea. By Thalassa, his watery female counterpart, he was the father of fish and other sea creatures. His granddaughter, Amphitrite, would later marry the god of the Mediterranean Sea, Poseidon. Oceanos and Poseidon later supersede Pontos in his roles as personification and god of the sea.

Myth describes the dangerous weather and storms on the Black Sea as Pontos' expression of grief at witnessing the eternal torture of Prometheus. Only Orpheus is said to have been able to calm the Black Sea, by beguiling Pontos with his music.

Ancient Greek cosmology viewed Pontos as the sea that bordered the extremities of the world, and thus was also the entrance to the underworld or Hades. For that reason, the Black Sea was also known as the entrance to Hades. Pontos was seen as the origin of all rivers, even those in the underworld such as the Styx.

In Greco-Roman mosaics, Pontos, or Pontus, is depicted as a giant head with a watery-gray beard and crab-claw horns rising from the sea. In a Roman sculpture of the 2nd century CE, Pontos is depicted rising from seaweed, grasping a rudder with his right hand and leaning on the prow of a ship. He wears a mural crown and accompanies Fortuna as twin patron deities of the Black Sea port of Tomis in Moesia.