A nonlinear three-dimensional time-domain performance model has been developed for a floating axisymmetric point absorbing WEC. This model employs a set of linear partial differential equations, in the form of a state-space model, to replace the convolution integrals needed to solve for radiation reaction. Linear time-domain results are verified against predictions from a frequency-domain model. Nonlinear time-domain predictions are compared back to frequency-domain and linear time-domain predictions to show the effects of some linearization assumptions. A simple resistive control strategy is applied throughout these scenarios.