Abstract: There is described an apparatus for inclusion in a ship comprising a mass (10), that is vibrationally coupled to the ship's hull (12) such that movement of the mass is dampened. The mass (10) is so sized and located as to, when in use it reduces the fundamental and/or harmonics of a transverse two node mode of wave-induced vibration in the ship's hull (12). There is also described an apparatus for inclusion in a ship comprising a mass (10) made up in part of the tackle or fitments of the ship, which also are vibrationally coupled to the ship's hull (12) by a damping such that movement of the mass (10) is dampened so as to thereby, when in use, reduce vibrations in the ship's hull (12). In a preferred embodiment the mass (10) is at least in part a chain locker and that portion of the chain stored therein. By reducing vibrations in the ship's hull (12) significant stresses may be relieved and the performance of the ship enhanced.