RedactedNarrative: THIS CRASH OCCURRED AS VESSEL ONE WAS TRAVELING DOWNSTREAM ON THE OSAGE RIVER, WHEN IT TRAVELED OVER THE TOP OF THE MARIOSA LOCK AND DAM. THE OPERATOR THOUGHT THE WATER LEVEL ON BOTH SIDES OF THE DAM WERE EQUAL, BUT AS HE APPROACHED THE DAM HE REALIZED THERE WAS A FIVE OR SIX FOOT DROP ON THE OPPOSITE SIDE. IT WAS TOO LATE TO TURN AROUND AND V1 TRAVELED OVER THE TOP OF THE DAM.  WHEN V1 WENT OVER, OPERATOR 1 HIT HIS FACE ON THE STEERING CONSOLE AND HIS LOWER BACK WAS INJURED. THIS ALSO CAUSED A WELD ON THE TRANSOM TO BE DAMAGED.