Sort of long story short, the Hindu Noah found a tiny fish in his well, and the fish asked him to move it to a bigger pond, and each day, the fish grew bigger, and asked to be moved to a bigger body of water, until H. Noah carted him over to the ocean. By this time, the fish had grown to the size of an ocean liner, and it confessed to him that it was really one of the avatars of Vishnu, and asked him to build a boat to house a lot of animals, as the world was about to be flooded due to the machinations of an evil asura whom his other avatar of a boar-headed giant was about to deal with.