I used to belive that 100% air humidity means, air is that humid that it is actually water and therefore the regarding region is completely underwater.
A childhood belief about weather

others believed things like this
- I used to think the Black Country region in the UK was called that because everyone lived in darkness there.— K
- i used to believe that pools had underwater doors that sharks were going to swim out of.— marky
- I used to believe eating fish enables me to live underwater and eating veggy makes me prettier!— Melody
- I thought that hydrogen was pure water (since I knew hydro- meant water) and H2O was impure some how— Hexetic
- I used to believe that if i splashed water on the wall during a bath, the water would turn into spiders— justin
- I used to believed that "approximately" actually means "important".Anon