The horizontal and vertical motions of a nonlinear spherical buoy, excited by synthetic ocean waves within a wave flume, is numerically and experimentally investigated. First, fluid motion in the wave tank is described using Airy's theory, and the forces on the buoy are determined using a modified form of Morison's equation. The system is then studied statically in order to determine the effects of varying system parameters. Numerical simulations then use the governing equations to compare predicted motions with experimentally observed behavior. Additionally, a commonly used linear formulation is shown to be insufficient in predicting buoy motion, while the nonlinear formulation presented is shown to be accurate.