In a recent work, explicit formulas of smooth time-varying state feedbacks which make the origin of a model of an underactuated surface vessel globally uniformly asymptotically stable are proposed. In the present work experimental results are presented where these control laws are implemented for control of a model of an offshore supply vessel in order to investigate the values and limitations of the theoretical results. In the experiments the ship is exposed to perturbations including unmodeled dynamics, waves, currents and measurement noise. The experiments indicate that the control system possesses some robustness to these perturbations, something which complies with theory. The experimental results suggest that unmodeled ship dynamics and environmental disturbances should be taken into account in the controller design for practical implementation.