A transducer position adjustment method, performed to compensate for initial ultrasonic beam alignment error, includes the steps of providing a manipulator of an ultrasonic immersion testing system having a pointing direction and supporting a transducer generating an ultrasonic beam, providing a calibration body defining a target thereon, immersing the transducer of the manipulator and the calibration body in a coupling fluid in an immersion tank of the system, setting the manipulator initially at a first position such that the pointing direction of the manipulator is aligned with the calibration body target at known coordinates, and adjusting the manipulator subsequently to a second position such that the ultrasonic beam of the transducer is brought into alignment with the calibration body target at the known coordinates for initiating an inspection of a test object after replacing the calibration body with the test object.