RedactedNarrative: VESSEL 1 WAS APPROCHING THE SHORELINE OF THE BIG ISLAND ON THE SOUTH SIDE TO BEACH AND SWIM.  AS VESSEL 1 APPROACHED THE SHORELINE, APPROXIMATELY 30 FT. FROM THE WATERS EDGE, VICTIM 1 STOOD UP ON THE BACK SEAT PORTION OF THE VESSEL AND DOVE IN.  THE WATER WAS APPROX. 2 FT. DEEP AND VICTIM 1 SUFFERED MAJOR INJURIES TO HIS NECK AND HEAD.  PASSENGER 1 AND 2 JUMPED IN AND PULLED THE VICTIM TO THE WATERS EDGE TO KEEP HIM FROM DROWNING.  VICTIM 1 WAS CONSCIOUS BUT DID NOT HAVE ANY FEELING FROM HIS NECK DOWN.  PROPER AUTHORITIES WERE CALLED AND AIR EVAC LANDED ON SCENE FOR TRANSPORT.  VICTIM 1 WAS AIRLIFTED TO MERCY HOSPITAL IN FT. SMITH ARKANSAS. AREA OF THE ACCIDENT WAS APPROX 2 MILES NORTH OF LADY BIRD LANDING NORTH RAMP AND APPROX 30 FEET SOUTH OF SOUTH SHORELINE OF THE BIG ISLAND.