Nonlinear behaviour of wave energy converters in power production mode can be relevant depending on the sea-state, the geometry or the motion of the device. Therefore, mathematical models used to simulate the behaviour of the device may need to include nonlinear effects. This paper studies the impact of modelling nonlinear Froude–Krylov forces by computing the pressure over the instantaneous wetted surface and uses a nonlinear wave theory (the Rienecker–Fenton’s theory) including nonlinear free-surface boundary conditions, to be more consistent with the computation of nonlinear Froude–Krylov forces. First, geometric nonlinearities are studied through the consideration of two heaving point absorbers with different geometrical characteristics: a truncated cylinder with a constant cross-sectional area (CSA) and a sphere with a non-uniform CSA. Then, nonlinearities related to the body dynamics are studied by applying a latching control strategy, which highlights the effect of nonlinear dynamics, showing the necessity to consider nonlinear WEC models as a basis for model-based control design. Results show that the performance of a standard fixed-time latching strategy drops considerably when applying nonlinear dynamics, so the fixed-time latching strategy is modified implementing the adaptive latching strategy. The impact of nonlinear Froude–Krylov forces is demonstrated to be low for devices with a constant CSA, but significant for devices of varying CSA.