Answer to Question #310463 in Human Anatomy and Physiology for sheba

Question

If the products of respiration are carbon dioxide and water, why don’t we drown when we breathe?

Answer 1

Humans cannot breathe underwater because our lungs do not have enough surface area to absorb enough oxygen from water, and the lining in our lungs is adapted to handle air rather than water. In the case of hydrogen and oxygen gas, if you react them together one way you get liquid water (H2O). The reason we cannot breathe liquid water is that the oxygen used to make the water is bound to two hydrogen atoms, and we cannot breathe the resulting liquid.