THE ALASKA STATE TROOPER PILOT LANDED AT AN OFF AIRPORT SITE ADJACENT TO A RIVER TO APPREHEND AN APPARENT VIOLATOR OF THE STATE'S FISH AND GAME LAWS. THE LANDING SITE WAS COVERED WITH LONG GRASS AND POCKETS OF WATER. FOLLOWING THE ENFORCEMENT ACTION, THE PILOT ATTEMPTED TO TAKEOFF FROM THE APPROXIMATELY 1,200' LONG 'STRIP'. THE AIRPLANE FAILED TO BECOME AIRBORNE PRIOR TO REACHING AN AREA OF TALLER GRASS AND DEEPER WATER, AND THE PILOT ELECTED TO ABORT THE TAKEOFF. THE AIRPLANE SUBSEQUENTLY GROUND-LOOPED AND NOSED DOWN. NO PRETAKEOFF MECHANICAL ANOMALIES WERE CLAIMED OR DISCOVERED.