Water is arguably the most important biological molecule, as it is the solvent and general environment for all living systems, as we know them.
Most of the unusual properties of water can be traced to hydrogen bonding. As is seen below the water molecule can particpate in four hydrogen bonds with other molecules. This loose matrix of molecules is what gives a low molecular weight molecule such a high boiling point.
The individual OH bonds are quite dynamic; the hydrogens are exchanging between water molecules at a very rapid rate. This exchange has been demonstrated by mixing normal water (H2O) and heavy water (D2O). After a brief time an equilibrium mixture of HOD is found. The exchange process also accounts for the acid/base character of water. The transfer of a hydrogen from one water molecule to another creates, in the transferring pair, a hydronium (H3O+) ion and a hydroxide (OH-) ion. At the beginning of the animation, the ionization process is seen, creating the hydronium and hydroxside ions. The last exchange is a neutralization as the transfer of a hydrogen from the hydronium to the hydroxide reforms two water molecules. The other exchanges are random throughout the bulk of the water, with no not change in ion concentration.
Remember, in distilled water [Hydronium ion] = [Hydroxide ion] and their product, Kw, is 10(-14).