Second-order Moller-Plesset perturbation theory has been used to calculate the interaction energy between a water molecule and acenes as large as C96H24. The results of these calculations lead to an estimated value of -5.8 +/- 0.4 kcal/mol for the electronic binding energy of a water molecule with single-layer graphite. This value is comparable to the -5.0 +/- 0.1 kcal/mol binding energy of the hydrogen bonded water dimer, suggesting that the water/graphite interactions will play an important role in determining the structure of water on graphite, as well as of water inside carbon nanotubes. The present estimate of the binding energy of a water molecule to a graphite sheet is appreciably larger than those previously reported in the literature.