An acoustic dataset collected during the 1983 Florida Straits Experiment [H. A. DeFerrari and H. B. Nguyen, J. Acoust. Soc. Am. 79, 299 (1986)] is modeled using the normal-mode acoustic model SWAMP (shallow water acoustic modal propagation by M. F. Werby and N. A. Sidorovskaia) and parabolic acoustic model RAM (range-dependent acoustic model by M. Collins). The goal of the computer simulation is to get systematic studies of the influence of range-independent and range-dependent environments on the received pulse structure observed in the experiment. In the experiment the pulse, with central frequency 460 Hz, was sent through three different shallow-water acoustic channels with surface and bottom ducts. It was found that the surface duct generated an important temporally stable effect for the range-independent environment. At a range 42 km, six surface trapped precursors were observed. The range-dependent propagation channel implied that the energy transfers between modes made the effect less pronounced when only three weak precursors could be seen. The obtained systematic studies can be important in constructing inverse tomography techniques, in predicting sea-bed characteristics, and in better understanding the influence of the ocean ducts on sound propagation.