Yes i've heard of them the Nephilim.
I suppose they were the aliens, seen as "Gods" by the human population.
Some say the "flood" is a recurring event that happens on Earth
every 3600 years, sometimes major, sometimes minor, and the aliens took to their spaceships to escape it, and did not let the humans know because they wanted to get rid of them. One of these aliens did however save genetic material (not the ark 2 by 2) of humans and animals for later recreation. This became the story of the ark.
Revelations describes the catastrophe, and the writer (one of the lucky ones taken up with the aliens) records looking at Earth from above seeing it flooded completely and then later when the waters receded, become a "new earth".

I wish i could time travel with a video camera and much film to see what really happened, even as far back as 50,000 years ago, which is when they the aliens are supposed to have landed.