A method of modeling an aquatic environment or locating an acoustic source in the aquatic environment. A range-dependent medium is approximated in terms of a series of range-independent regions and obtaining single-scattering solutions across the vertical interfaces between regions. One or more acoustic waves are propagated from a known acoustic source through the range-dependent medium to one or more known seismoacoustic receivers to model iteratively the various solid and liquid layers of the range-dependent medium. Alternatively, one or more acoustic waves are reverse-propagated from one or more known seismoacoustic receivers through the range-dependent medium to determine whether an acoustic source is present within a user-defined range.