A rectangular aluminium plate vibrating in air or in contact with water is investigated. The plate is bolted to a wall of a rectangular Plexiglas container. Some modal analyses are firstly realised in order to verify the effects of different water levels and of the control components on the modal parameters. A filtered-x least mean square (FXLMS) adaptive feedforward algorithm is then applied to the system, realising structural vibration control in linear field with a SISO approach on the first vibration modes of the plate in presence of tonal primary disturbance.