This website contains age-restricted materials including nudity and explicit depictions of sexual activity.
By entering, you affirm that you are at least 18 years of age or the age of majority in the jurisdiction you are accessing the website from and you consent to viewing sexually explicit content.
This relates to the bible concept of firmament, flat earth and separation of waters, as in genesis when it says god separated waters above and below.
The nomads knew wells, rain, islands, tides and flooding rivers, so the world they conceptualised was one where God moved water above and below to reveal dry land. As such in the story it seemed logically consistent to allow massive amounts of water to come from above and below returning the world in what they considered a previous, erased state to reboot it.