This paper is concerned with the distributed consensus problem of multiple underactuated surface vessels, where the number of the vehicles actuators is fewer than the vehicles degrees of freedom. To cope with the coupling of unactuated and actuated states, a state transformation is proposed to change the format of the system to a cascade nonlinear system, and an appropriate switching controller is designed based on the stability properties of cascade systems to make the vehicles to reach a consensus. To illustrate the performance of the proposed approach, simulation results are provided.