Satyavrata, the king of pre-ancient Dravida and a devotee of Vishnu, was washing his hands in a river when a little fish swam into his hands and pleaded with him to save its life.
He put it in a jar, which it soon outgrew. He then moved it to a tank, a river and then finally the ocean but to no avail.
The fish then revealed himself to be Vishnu and told him that a deluge would occur within seven days that would destroy all life.
The fish told Manu that at the end of Kali yug, the mare who lived at the bottom of the ocean would open her mouth to release a poisonous fire; the fire will burn the whole universe, gods, constellations and everything.
The seven clouds of doomsday would then flood the earth until everything was a single ocean. Therefore, the fish instructed Satyavrata to take "all medicinal herbs, all the varieties of seeds, and accompanied by the seven saints”along with the serpent Vasuki and other animals and board a boat that the gods had built.