This book presents a theoretical treatment, as well as a summary of practical methods of computation, of the forces and moments that act on marine craft. Its aim is to provide the tools necessary for the prediction or simulation of craft motions in calm water and in waves. In addition to developing the required equations, the author gives relations that permit at least approximate evaluation of the coefficients so that useful results can be obtained. The approach begins with the equations of motion for rigid bodies, relative to fixed- and moving-coordinate systems: then, the hydrodynamic forces are examined, starting with hydrostatics and progressing to the forces on a moving vehicle in calm water and (after a review of water-wave theory) in waves. Several detailed examples are presented, including calculations of hydrostatics, horizontal- and vertical-plane directional stability, and wave-induced motions. Also included are unique discussions on various effects, such as fin-hull interactions, numerical stability of integrators, heavy torpedoes, and the dynamics of high-speed craft. The book is intended to be an introductory level graduate text and a reference for the practicing professional.