The Manu of our era, Vaivasvata, carries Hindu tradition's deluge story. Its oldest telling is in the Shatapatha Brahmana: a small fish comes to Manu's hands and asks for protection, growing stage by stage from a jar to a trench to the ocean, and in return warns him of the coming flood, instructing him to build a ship. When the waters rise, the fish, now immense and horned, tows the ship to a northern mountain, and Manu, sole survivor, becomes the father of renewed humanity.
The Puranas retell the story with the fish revealed as an avatar of Vishnu, the Matsya avatara, first in the classical list of ten, and add that Manu preserved the seeds of all beings and the Vedas themselves through the dissolution. The parallels with the Mesopotamian and biblical flood narratives, a warned survivor, a vessel, a mountain landfall, renewed creation, have been discussed since the nineteenth century, though the Indian version is distinctive in what the flood means: not divine punishment of wickedness but the ordinary hinge between cosmic periods, dissolution and renewal operating on schedule. That reframing is the manvantara doctrine doing its work. Catastrophe is domesticated into rhythm; the flood is not the end of the world, only the end of a shift, and the survivor is not a saved sinner but the incoming administrator of the next age.
Sources The Satapatha Brahmanatranslated by Julius Eggeling with Vishnu PuranaAnonymous