This paper addresses the design and experimental validation of a trajectory tracking controller for an underactuated hovercraft with unmeasured linear velocity and subject to time-varying disturbances. The unmeasured linear velocity and disturbances are recovered by designing nonlinear observers. A control law is proposed that, in closed-loop with the velocity and disturbance observers, can robustly steer the hovercraft toward and stay within a neighborhood of a reference trajectory. To demonstrate the performance and robustness of the proposed control strategy, we present and analyze experimental results obtained with a model-scale hovercraft.