The evolution of fluidity in glassy water films has been investigated in the temperature range 125-150 K on the basis of isothermal TOF-SIMS experiments. The initially uniform film dewets the Ni(111) substrate above 135 K, as revealed from the sputtering of Ni+ ions. The onset of dewetting marks a temperature for the structural relaxation in the glass-liquid transition, but it requires anomalously long aging time (4-20 min for 150 K > T > 135 K). The delay of structural relaxation relative to the onset of translational molecular diffusion (above 135 K) should be characteristic of supercooled liquid phase. (c) 2005 Elsevier B.V. All rights reserved.