Why can't we breathe underwater?
Humans can't swallow and breathe at the same time once they surpass 9 months of age, and we can never breathe underwater. Why not?
from Brain Stuff
Key Facts In This Video
Because of water's chemical composition, it can't be breathed by humans. (1:10)
Fish are more easily able to consume oxygen underwater because of their gills and cold-blooded nature. (2:06)