Acoustic reflection coefficients for reflection from ocean bottoms are sometimes calculated for postulated models of the bottom structure. A published example, using a model based on geophysical data, is examined with attention to possible simplification and to the physical links between model and computer output. It is shown that calculated results at small grazing angles have a physical cause and can be well approximated by a simpler model. It appears, however, that at larger angles the results are not physically reasonable. The cause is that a commonly used ’’pseudolinear’’ gradient of sound speed is unphysical in a half space, because at a certain finite depth the sound speed becomes infinite, and imaginary at greater depths. A physically reasonable profile of sound speed is proposed as a substitute and expressions for the reflection coefficient are derived in the approximation of vanishing absorption. At that stage, the expressions are considerably simpler than those of the published example. An extension incorporating absorption is planned.Subject Classification: [43]30.20, [43]30.30.