  Hydrophobic force, interfacial tension, transverse density profile in
confined water system are addressed from first principles of statistical
mechanics in a lattice model for water. Using molecular mean field theory
technique we deduce explicit expressions for each of the above mentioned
phenomena and show that hydrophobic force is a manifestation of Casimir-like
effect due to hydrogen bond fluctuations in confined water. It is largely
influenced by the long range correlations of orientational fluctuations. All
the computations are parameter-free and we compare favorably with results of
molecular dynamics simulations and experiments.
