The interaction energy of a water molecule with a mercury surface is calculated on the basis of a relatively simple model. The interaction energy of an isolated molecule and the metal surface is evaluated in terms of the water-metal surface distance and of the degree of dipole orientation. The most probable equilibrium orientation of the water dipole corresponds to the 0°a ngle at an operational equilibrium distance of 1.85 X 10'8 cm. The calculated total energy coincides with the most reliable experimental value.