text: In the gas phase, a single water molecule has an oxygen atom surrounded by two hydrogens and two lone pairs, and the  geometry is simply described as bent without considering the nonbonding lone pairs.
  However, in liquid water or in ice, the lone pairs form hydrogen bonds with neighboring water molecules. The most common arrangement of hydrogen atoms around an oxygen is tetrahedral with two hydrogen atoms covalently bonded to oxygen and two attached by hydrogen bonds.  Since the hydrogen bonds vary in length many of these water molecules are not symmetrical and form transient irregular tetrahedra between their four associated hydrogen atoms.