In this paper, a new approach for robust control of a surface vehicle is presented. This approach uses a sliding mode controller with an additional robust term. A nonlinear dynamic model which is complicated by environmental disturbances is presented for a surface vehicle, dividing the model into the rigid-body portion, and a portion containing disturbance terms that the robust controller will reject. Following that, a robust approach based on sliding mode controller is developed for tracking desired trajectories in finite time while compensating for disturbances such as hydrodynamics, wind, wave, and currents based on Lyapunov-type stability analysis. Finally numerical simulation results are shown to demonstrate the validity of the proposed controllers.