This work presents our research results on the capability of passive source localization using a towed multi-module array in underwater acoustic environments. We developed new Cramer-Rao Lower Bound (CRLB) results for assessing the array's source localization capability under environmental uncertainties, such as array modules' positions and acoustic-field's spatial coherence. We also developed a two-stage approach and provide details for passive ranging by utilizing data either non-coherently or coherently, depending on the availability of spatial coherence in the received data from multiple modules of towed array.