Ark of Humanity: God flooded the earth to annihilate humanity's sins. What if that sinful race didn'

Under the depths of the ocean one boy has raised himself, until the day when he meets a dark-skinned man with news that will change the lives of his civilization forever. Now he must save his people from another empire of water dwellers bent on enslaving the oceans and torturing his peaceful realm. Yet another question is posed as he learns that his people are descended from humans that lived on the land above the ocean; a people that were destroyed by floods made by the rage of God. If they have to, in order to escape, will they be able to breathe air and join whatever is left of the world above the waters? What would they find there? Is the mythological Noah still alive?