A challenging problem in bottom-interacting ocean acoustics and marine seismology is to accurately describe environmental variability in a computationally feasible model. Wave field predictions are often difficult in environments with strong range dependence, with rapid bathymetric variations, with multiple scattering regions, with interface waves at fluid/solid boundaries, and/or with shear waves in the bottom. In this presentation, we are using an existing three-dimensional spectral-finite-element code (SPECFEM3D, distributed and supported by the NSF funded program, Computational Infrastructure for Geodynamics), originally developed for simulations of seismic wave propagation at the local or regional scale, to bottom interaction problems in underwater acoustics. Recent developments of the SPECFEM3D model include full compressional attenuation in elastic media and improved transparent boundary conditions. Numerical results from SPECFEM3D are compared with wave fields simulated using acoustic propagation model based on the parabolic equation (PE) method, for a 10 Hz broadband acoustic pulse propagating in the deep ocean. The importance of out-of-plane scattering and bottom shear properties on resulting wave fields are investigated.