Static and dynamic properties of a layer of water molecules on top of a graphite surface are studied by means of molecular dynamics simulations. The water molecules are described by a simple point charge flexible model, and the graphite is taken to be a set of featureless parallel sheets separated 3.4 Angstrom in the z direction. Our results indicate that, even at the lower temperatures considered, the water layer is not flat, with some hydrogen atoms pointing perpendicularly to the surface plane. The O-H stretching frequencies are also different than those of bulk water, appearing a new peak in the simulated spectra at a frequency approximately 200 wave numbers higher than the main peak. This peak is associated with the presence of non-H-bonded molecules.