A Perforated-ball Velocity Meter (PVM) device measures the wave induced forces on cantilevered ball-tube assembly and the wave kinematics is computed from these forces by solution of an inverse problem given by the Morison's equation. The drag and inertia coefficients of both the ball and the tube are experimentally determined and the forces on both the ball and the tube are used in the inverse Morison problem. The behaviour and convergence of the numerical scheme for this inverse problem has been studied in detail. The laboratory experiments conducted using the PVM and the measured kinematics have been compared with calculated kinematics obtained from the free surface elevation measurements using the linear wave theory and the Wheeler stretching theory. The comparisons have been satisfactory. It is also shown that the kinematics measured by the PVM can yield the free surface elevation with good accuracy. (C) 2000 Elsevier Science Ltd. All rights reserved.A Perforated-ball Velocity Meter (PVM) device measures the wave induced forces on a cantilevered ball-tube assembly and the wave kinematics is computed from these forces by solution of an inverse problem given by the Morison's equation. The drag and inertia coefficients of both the ball and the tube are experimentally determined and the forces on both the ball and the tube are used in the inverse Morison problem. The behaviour and convergence of the numerical scheme for this inverse problem has been studied in detail. The laboratory experiments conducted using the PVM and the measured kinematics have been compared with calculated kinematics obtained from the free surface elevation measurements using the linear wave theory and the Wheeler stretching theory. The comparisons have been satisfactory. It is also shown that the kinematics measured by the PVM can yield the free surface elevation with good accuracy.