The formula for water, H2O, is comprised of covalent bonds. These incredibly strong bonds hold the hydrogen and oxygen molecules together. Water molecules are polar molecules, which maintain a bent shape.
Water is comprised of two hydrogen atoms and one oxygen atom. The structural formula for water is bent with 107.5 degrees between each atom. Water maintains this structure due to the tetrahedral arrangement of the electrons around oxygen. The oxygen molecule has lone pair electrons that form an electron cloud around the molecule. The lone pairs are negatively charged and push the two hydrogen atoms closer together in order to maintain the bent molecular shape.