Many ancient cultures have their myths. My article is to analyze the story of the flood and draw some tentative conclusions therefrom.
The tenth Manu (from which are derived the English words man and manual) caught a small fish and to his surprise the fish spoke to him and promised to protect him from the coming deluge, if he spared it. Manu put the fish in a small water filled container and fed it. The fish grew by leaps and bounds and Manu kept transferring it to larger and larger containers. It grew to immense size and warned him to build a big boat and tie it to the fin of the fish and sail towards the northern mountain. The great flood came and it was relentless and the fish which was Vishnu's Matsya Avatar saved humanity from extinction. Ziusudra was a good king of Sumer and the god Enki warned him that the remaining gods had determined to destroy mankind. He told Ziusudra to build a big boat. The flood came and humanity was saved. Noah was warned to build a big boat and take a pair of all animals on to the boat. The boat was to go to Mount Ararat and anchor at its top which was flooded.
These three ancient cultures have very similar stories about the great flood. There are no great rivers to cause such major floods in biblical Israel but we know that the Hebrews trace their origin to Abraham of Ur which is in Mesopotamia. While the Tigris and Euphrates flood and frequently change course, their floods are not that massive. An interesting aside is the English verb Meander meaning wander aimlessly comes from the name of a Turkish river notorious for changing its course. The Indus and Ganges do flood but nothing like the deluge described by Manu.
The great deluge occurred around 5000 BCE when the Mediterranean broke into the Black Sea. This led to migration of the littoral inhabitants in various directions to Ukraine, Anatolia, Syria and Mesopotamia. These people carried with them the indelible memory of the flood and its myth.
The Akkadians carried the story because to them Sumerian was what Latin was to the Europeans. All Akkadian scribes had to learn Sumerian, a dead language, just as all educated Europeans learnt Latin in the Middle Ages. The Christians incorporated the myth because they absorbed the Old Testament since their god was Jewish by birth. Religions that arose later did not incorporate the myth. Zoroastrianism which has common origins with the Hindus omitted the myth as did, Jainism, Buddhism and Sikhism. Similarly Islam which is a sort of mixture of Judaism, Christianity and some local Arabian customs omitted the myth.
What is interesting is that the Greeks do not have the myth even though their derivation is Indo-European linguistically and the Egyptians with their annually flooding Nile do not have the myth. Possibly Greece was settled by later immigrants from Anatolia to whom the myth had little historical value. Zeus and his thunderbolt correspond to Indra and his Vajra. The other Greek myth identical to the Indian one is the birth of Athena, the goddess of wisdom from the head of Zeus like that of Saraswati from the head of Brahma.
Another common myth between the Sumerians and Hindus is that of the Seven Sages. The Sumerians believed that their knowledge and civilization arose from the Seven Sages. Hindus have the myth of the Sapta Rishis who were more powerful than Indra. It is from the Sumerian calendar that we still have the seven day week. They also did not have a decimal system which India invented with the zero. Their base of counting was sixty instead of ten and that is why we still have sixty seconds to a minute, sixty minutes to an hour and 360 degrees in a circle.
I know that the Hindutva brigades and some recent DNA studies seem to point that over six millennia the Indian DNA does not reveal outside genes. They claim that the Mitannis and Hurrians migrated from India to Syria and carried Sanskrit and their gods Indra, Varuna and the Nastutyas with them and this is why the Hittite treaties with the Mitanni around 1500 BCE mention these gods as witnesses and their manual on horses contain Sanskrit colors. The undiscovered Mitanni capital in Syria was named Vasu-khanni meaning rich earth. There is another problem that horses are not indigenous to India and Maria Giambutas has shown that the horse was domesticated first in Ukraine. The trees described in the Rig Veda are often not indigenous to India. For me even if the newer Hindutva point is correct it doesn't explain the Flood myth. It is also true that the Vedic religion with its rituals and sacrifices was more primitive as compared to the more intellectual Upanishadas and Brahman which evolved later, just as the more refined Sanskrit was clearly the work of Yaska, Panini and others which occurred in Northwestern India (currently Pakistan and the Indian north. The only known major migrants from India to Europe are the gypsies and that occurred much later.
To me there is a serious likelihood that the progenitors of the Hindus, Hebrews and Sumerians lived on the shores of the Black Sea around 5000 BCE and migrated to Anatolia, Syria, Mesopotamia and subsequently to Israel and India sometime later.