Parameter studies are interpreted to determine the dependence of bottom reflection loss (RL) from the ocean floor on subbottom parameters. The emphasis is on examining thin sediment layers for which sediment shear (S) wave excitation is important. RL is obtained from a numerical model which includes sedimentSwave propagation. The subbottom structure investigated has a single, horizontally stratified (solid) sediment layer with parameters typical of a high porosity, deep sea sediment overlying a semiinfinite homogeneous (solid) substrate. Subbottom parameter variations are constrained by available geophysical estimates. Homogeneous layers and layers with constant gradients are also investigated. The relationship between subbottom parameter accuracy and the uncertainty in calculated RL is addressed by making variations about a typical parameter set.