A picture of the Flood:
After the blinding light it rained for weeks and waters from below raised too. When the torrential rains stopped Earth was a waterworld; it rained billions tons of dust too; from space and from fierce volcanoes spitting it. Some weeks later the waters had filtered through downwards leaving muddy continents. Aquatic animals like fish and little animals like insects were not comfortable_ quite uncomfortable indeed_ but had not much of a problem to live on. Some animals survived despite have been buried for... years in a sort of hibernation. The very low levels of oxygen (much of the water came from hydrogen firing the atmosphere
http://www.varchive.org/itb/hydrox.htm and lightning combined oxygen into nitrates and into sulphur), relatively high levels of hydrogen sulphide (the activity of anaerobic organisms like sulphate reductors went tenfold) and cold weather made it possible. Normally cyanobacteria and the like would have restored oxygen levels in less than a year but in the cold and relatively dark world took over a hundred years. Some people thought the survivors (probably less than 50 humans) were the first humans and had been created from the mud or clay; plants and fungus were "created" de novo as well, in this case only the seeds had to self-preserve. If the world is many millions of years old probably wasn´t the first global flood nor the second nor the third... maybe not even the first since some human is around. The cosmic order changed after the Flood...
The Hopi myth I posted above speaks of a global catastrophe before the Flood:
The world had posts at the poles (Birkeland currents?), once the posts "broke" and Earth spun away wildly freezing completely. Some time afterwards the posts were restored and so life. That doesn´t sound magic or fantasy, that pretty much sounds science! A good occasion to refuge in some warm cave. This was (if not a made up story there must be some evidence of global glaciation in the last, 40,000 years?) most likely an episode of orbital chaos. No one knows whether these happen once per thousands years or once per million years or even less often.