We have used a new low‐energy electron diffraction (LEED) detector, that features a low beam current electron gun, to investigate for the first time the LEED intensities arising from a water‐surface adsorption system. H2O adsorption structures are very sensitive to electron radiation damage. A disordered monolayer of H2O molecules is formed on Pt(111) at 160 K. Upon further exposure an ordered multilayer film is grown that yields new diffraction spots. The periodicity of the diffraction pattern of the multilayer structure is compatible with the model of a molecular ice crystal. Preliminary intensity versus energy spectra of the ‘‘ice crystal’’ are presented. The film thickness is estimated to be well above 10 Å.