Water

Water is a tasty liquid which all of the human race requires to survive. Your body is made up of about 70% water, and so a lack of this chemical substance would result in flopping skin and onion skin weathering. Water is made up of two hydrogen atoms to one oxygen atom, and thus the chemical symbol of water is H2O. Because there are oxygen atoms, it is possible to breathe underwater, but only if you are floating upside-down. And only 3.14159265 of this post is true. Well. Perhaps a bit more.