WHILE BACKING MY BOAT INTO ITS PARKING SPOT, I PUT THE VEHICLE IN PARK. WITH THE ENGINE STILL RUNNING, I GOT OUT OF THE VEHICLE TO UNHOOK THE BOAT TRAILER FROM THE TOW VEHICLE, LEAVING THE DRIVER'S DOOR OPEN. AS I TURNED THE TRAILER JACK TO LIFT BOAT TRAILER FROM THE TRAILER HITCH OF THE TITAN TRUCK, WHICH IS THE TOW VEHICLE, IT JUMPED OUT OF PARK INTO REVERSE, AND STARTED TRAVELING BACKWARDS. AS I ATTEMPTED TO ENTER THE TRUCK AND PRESS THE BRAKE, THE TREE NEXT TO THE VEHICLE CAUGHT THE DRIVER DOOR. BECAUSE I WAS HOLDING ON TO AND USING THE OPEN DOOR AS LEVERAGE WHILE ATTEMPTING TO ENTER THE CAB TO STOP THE VEHICLE, I WAS THROWN TO THE GROUND VERY CLOSE TO BEING RUN OVER BY THE DRIVER'S SIDE TIRE. THE DOOR WHILE PASSING OVER ME CAUSED A SEVERE ABRASION TO MY LEFT ARM. AS THE RESULT OF THE REVERSE MOVEMENT OF MY TRUCK CAUSED BY THE GEAR SHIFT JUMPING FROM PARK TO REVERSE, MY BOAT WAS PUSHED DOWN INTO A CULVERT, DAMAGE AT THIS POINT UNKNOWN. INSURANCE CLAIM PENDING; LIABILITY TO NISSAN CORPORATION TO BE INVESTIGATED. *JB