Operator of PWC had departed from the dock and got underway with one passenger. The operator stopped the PWC. When the operator accelerated, the passenger fell off the back of the PWC.  The operator noticed profuse blood in the water from the passenger.  The water jet had caused a  perforation/laceration to the rectum area. The injured passenger was assisted back onto the PWC and taken back to the dock. The injured passenger was losing consciousness. 911 was called and first aide was rendered.
Morris