In this paper molecular hydrodynamics is used to calculate the dynamic friction on the intramolecular vibrational coordinate of a homonuclear diatomic molecule dissolved in a simple liquid. The predicted dynamic friction is then compared to recent computer experiments. Agreement with the experimental dynamic function is obtained when the linearized hydrodynamics is modified to include Gaussian viscoelasticity and compressibility. The hydrodynamic friction on the bond appears to agree qualitatively very well, although quantitative agreement is not found at high frequencies. Various limits of the hydrodynamic friction are discussed.