An Underwater Vehicle-Manipulator System (UVMS) is a complex and highly non-linear multibody dynamic system used in Inspection, Maintenance and Repair (IMR) operations. Beyond the disturbances caused by the hydrodynamic forces, the UVMS is also subjected to the dynamic coupling between the Underwater Unmanned Vehicle (UUV) and the manipulator. This coupling affects the attitude and position of the UUV, which should remain stationary while the manipulator moves. The correct compensation of such coupling could be achieved through precise model-based control or, e.g., with signals produced by a force/torque sensor mounted between the UUV and the manipulator. However, the former approach is almost impossible to achieve, and the latter is very difficult to implement. Given these problems, this paper proposes a station-keeping control scheme based on Reactions Wheels (RWs) as inertial actuators for the attitude stabilization of a UUV under the action of the disturbances induced by the manipulator. The effectiveness of the proposed control scheme is validated here through numerical simulation, taking as a case study a planar UVMS consisting of a UUV and a two-link serial manipulator. The proposed control system provides better performance on the station-keeping when compared with a model-based decoupling controller. Moreover, it leads to lower energy consumption, which can increase the autonomous capabilities of the UVMS.