A method to isolate the forward scattered field from the incident field on an object in a complex environment is developed for the purpose of localization. The method is based on a finite-frequency perturbation approach, through the measurement of a data-based sensitivity kernel. Experimental confirmation of the method is obtained using a cylindrical tank and an aggregate of ping-pong balls as targets surrounded by acoustic sources and receivers in a multistatic configuration. The spatial structure of the sensitivity kernel is constructed from field data for the target at a sparse set of positions, and compared with the expected theoretical structure. The localization of one or a few targets is demonstrated using the direct-path only. The experimental observations also show that the method benefits from including later arrivals from the tank wall and the bottom/surface reverberation, which indeed enhance the localization.