Long ago during the Pralaya which took place at the end of the sixth Manvantara, when Brahmaa was about to sleep, the great Asura Hayagreeva stole the Vedas from his mouth. In order to restore them, Thou decided to incarnate as a fish.
Sage Satyavrata, the king of Dramila, was doing Tarpana in the waters of the river Kritamaalaa. In his joined palms, then, Thou appeared as an lustruous undescribable form of a shining tiny fish.
When the royal sage threw Thee in the water, seeing Thee very frightened he took Thee to his home in the kamandalu, the water vessel. In a few days, Thou outgrew the pot, the well, the tank and the lake.