Quasielastic neutron scattering (QENS) has been used to investigate the dynamical behaviour of H₂O in the superconductor Na_0.28CoO₂·yH₂O. The measurements were obtained at room temperature for a molar concentration of water, y = 1.3. From the analysis of the Q-dependence of the EISF and the line-width we found that the water dynamics can be well described by rotational motion that likely correspond to re-orientation of the H₂O molecule. We were also able to define a rotational correlation time of τ = 1.85 ps.