I don't do the maths. Sure enough though, the water molecule is pretty damned small; plenty small enough to fit inside a one micron capillary many times over - no worries there ...

Hydrogen: 2.34 Å ~ Oxygen: 2.92 Å

~ so a string of 43 million hydrogen atoms would be one centimeter long.

An important feature of the water molecule is that, because of the small size of the hydrogen atom, the hydrogen atoms are "buried" in the oxygen's cloud of electrons. The water molecule is essentially spherical, therefore, and nearly the same size as the oxygen atom. (Hydrogen is 80% the size the of Oxygen atom, yet Oxygen is 9/10 the size of a water molecule.)

"The truth of today was the heresy of yesterday. Therefore, dare." -- Immanuel Velikovsky.