EE WAS GETTING THE PREG POND LEVEL. HE WAS MOVING THE WEIGHT CONNECTED TO THE TAPE MEASURE. AS HE WAS DOING THAT, HE LOST HIS FOOTING AND TWISTED HIS ANKLE. FACTORS/REASONS: POND COVER IS A SLICK LINER; EE WAS NOT USING ANTI-SKID PADS THAT ARE STUCK TO THE POND COVER. LOST BALANCE; EE WAS NOT USING ROPE TIED TO TOP OF POND.