According to the Oahspe Bible, the flood was the sinking of the continent Pan (aka Mu or Lemuria) in the Pacific Ocean, and the reason was, it was overrun by people with bad genetics and only a few remained of the genetically enhanced line of humans. So to save those few they were informed to build ships, and when the waters rose, they were on the ships and floated away in five directions and guided by angels/aliens to land on those areas and start over there.