Research on tidal turbines has been mainly focused on the design for greater energy efficiency for the last ten years. However, achieving a reliable operation is becoming more and more crucial in current studies. This work presents a continuous monitoring of those turbines based on vibrations controls the control, this technique allows implementing predictive maintenance strategies. The vibration response is analysed in a laboratory test rig. That vibration can be produced by a phenomenon as frequent as a misalignment of the shaft as well as their consequences in the early production of partial rub of the rotor/stator. The response obtained shows that one can easily detect a vibration signal with a misalignment in the shaft of 50 μm. Also, the rub of the shaft/seal is detected with the increase of the dynamic stiffness of the system from 12,87 to 14,30 KN/m. Additionally, the resonance frequency also increases its value from 2400 to 2500 rpm. The application of this early detection on the watertight seal of a tidal turbine, would potentially avoid severe hazards in these equipment.