The flood occurred in conjunction with the periodic visits of the 12th Planet, which swings through the Earth's Solar System causing cataclysmic Earth changes such as pole shifts. The Flood occurred three pole shifts back, approximately eleven millennia ago. The shift prior to that had been slight, so that melting of the poles was slow and incomplete. Ordinarily each pole shift places the old poles in a position where they will quickly melt, facing the Sun. The pole shift ahead of the one causing the flood only moved the old poles slightly, so much of the ice was still remaining. Poles over land have constant runoff when they melt, and settle as the weight of ice presses down, but poles over oceans melt more from the bottom up, leaving caverns of ice honeycombed within as the water can support ice of odd shapes. Thus a vast body of thin ice stretched out over the southern ocean, over the location of the old pole. When the comet caused massive Earth movements this ice sheet fractured and fell into the water, causing a huge displacement and resulting massive wave. This wave was the flood, of legend worldwide.
Noah was given warning by the actions of inhabitants from the 12th Planet, visiting Earth. He observed their frantic preparations to leave, as they were keenly aware of the devastation that their passing planet caused on Earth, and could compute the closeness of the passage when their inbound planet was sighted. Unlike other passages, they were going to be in harms way due to the condition of the South Pole ice, which they had visited and checked upon. Uneasy, and being a highly Service-to-Other man, he gave The Call and received visits from a Spirit Guide who responded. He did indeed construct a boat to save himself, his family, and household animals. The story of Noah has been romanticized to include all the animals of the Earth, which doesn't take much logic to dispel. How big a boat was this? Where the wave was large, it did not cover the entire Earth. How could it? Thus, there was more drowning during this particular visit of the 12th Planet, but other than that, not much difference.