UNIT 1 WAS TRAVELING DOWN THE STONO RIVER WITH 2 PEOPLE ON BOARD. THE STEERING CABLE CAME LOOSE UNDER THE CONSOLE AND CAUSED UNIT 1 TO SUDDENLY TURN TO THE RIGHT THROWING BOTH PASSENGERS INTO THE WATER. UNIT 1 THEN STARTED CIRCLING AT APPROXIMATELY 30-35 MPH UNMANNED. THE VESSEL CONTINUED TO CIRCLE UNIT IT HIT A DOCK ABOUT 1/2 MILE UP RIVER FROM WHERE THE PASSENGER WERE THROWN OUT.