By using distilled water as the standard reflector, relative specular reflectance spectra in the 2- to 20-μm wavelength region of the infrared were measured for surface water samples collected from the San Francisco Bay, the Pacific Ocean, the Atlantic Ocean, the Great Salt Lake (Utah), the Dead Sea (Israel), and an effluent pit of a phosphate mine in central Florida. Phase difference spectra and spectral values of the complex refractive index were computed for each water sample by applying a Kramers--Kronig analysis to the relative reflectance spectra. Spectral values for the complex refractive index suitable for Mie scattering calculations were tabulated for each water sample. The reflectance spectra of the natural saline waters bore great similarity to spectra for individual aqueous solutions containing NaCl, K2SO4, NH4H2PO4, NaNO3, and NaHCO3. Chemical analyses of the water samples are also presented in tabular form.