Chloride ion solvation in supercritical water is investigated by computer simulations, including water polarizability explicitly. Comparisons are made between the TIP4P fluctuating charge and the original TIP4P models. Particular attention is paid to the density dependence of the equilibrium structural and transport properties. The chloride ion hydration number slowly decreases with density reduction in a similar way for both the fluctuating charge and the fixed-charge water models. The diffusion coefficients for the two models also exhibit a similar density dependence, except at the lowest density examined (0.05 g/cm(3)), where the chloride ion diffusion rate in polarizable water is significantly larger than that in nonpolarizable water because of a more rapid loss of the hydration shell in polarizable water at the lowest density. The remarkable similarity between the two models is related to the insensitivity of the local polarization in the first hydration shell to the bulk conditions. The results also suggest that the local viscosity rather than the long-range dielectric friction dominates the transport properties.