This paper describes the development of a position tracking system designed for a Remotely Operated Vehicle (ROV). The sensor package consists of an Inertial Measurement Unit (IMU) and a Laser-based Vision System (LVS). The LVS consists of two undewater Laser pointers and a single CCD camera mounted on the ROV. The LVS fuses data deriving from the projection of the laser pointers on the image plane while it tracks a target at the same plane using computer vision algorithms. The LVS calculates the position vector of the vehicle at a low frequency, with respect to the center of the tracked object. The IMU measures the accelerations and angular velocities of the vehicle at a high frequency. The fusion of the two sensors is based on a Multisensor Kalman filter where the measured acceleration and angular velocity of the IMU is fed directly to the filter. The result is the calculation of the position vector at a high frequency, which can be used for a smooth closed loop steering control of the vehicle. The integration of the system was proved successful through an extensive experimental procedure.