A good dynamics model is essential and critical for dynamic analysis of underwater vehicle. However, it is difficult to determine the hydro-dynamics forces, especially the added mass and the drag coefficients. In this paper, an experimental method has been used to find the hydrodynamics forces for a remotely operated underwater vehicle (ROV). The proposed method is based on the classical free decay test. The experiment was video captured, then processed by a Covariance Tracking MATLABTM computer program to determine the time history of the swinging angle of the model, then the values were numerically processed by least square method to determine the coefficients values, which compared with the simulation results obtained from well-established computational fluid dynamics (CFX) program. Thus, the proposed approach can be used to find the added mass and drag coefficients for other underwater vehicles.