In this paper, we continue our study on combining the matched field processing with the boundary integral equation (BIE) method of scattering theory to solve a sound source localization problem in a shallow ocean with a large inclusion which has a rigid boundary. We consider an enviroment where continuous waves (CW) are produced by a sound source, scattered by the inclusion, and then received by a hydrophone array. The symmetry of the waveguide is destroyed by the existence of the inclusion, and a proper procedure is therefore required to avoid the mismatching. We present a numerical scheme which makes use of the separation of the source and the detection array, and a BIE method. The separation greatly reduces the computation load. The BIE method preserves a certain accuracy on one hand and minimizes arithmetic operations on the other. Some numerical simulations using this scheme are presented.