The hindered translational motions, the librations around the principal axes, and the intramolecular vibrations have been calculated from molecular dynamics simulations of water by Fourier transformations of the corresponding velocity autocorrelation functions for ail possible hydrogen-isotope-substituted molecules at room temperature. The flexible BJH model for water has been employed in the simulations. The frequencies for the hypothetical liquids HDO, HTO, and DTO as well as the stretching vibrations of T2O are predicted.