M. Warburton, J.M. Ablett, J.-P. Rueff, P. Baroni, L. Paolasini, L. Noirez We examine the influence at room temperature of the deposit of a water layer on the phonon dynamics of a solid. It is shown that the water wetting at the surface of an Alumina monocrystal has deep effects on acoustic phonons, propagating over several hundred µm distance and taking place on a relatively long time scale.