I heard the canopy theory, too, many years ago. Sounds plausible.
To me the most interesting thing about the Noahic period is the very reason for the flood. And that was the genetic contamination of mankind.
Good point.
That genetic contamination might well have also been aided by susceptibility to radiation (water vapor canopy or some other mechanism pre-Flood screening out its DNA-crushing destruction), higher air pressure, and God lifting His protective hand from biological contaminants.