This is the moment four men were rescued from boat at it teetered precariously on the edge of a 130ft drop off the side of a dam. National Sea Rescue Institute (NRSI) crews were dispatched to the Grootdraai Dam in Mpumalanga, South Africa, on Monday (29 December) after the boat suffered motor failure and drifted toward the edge of the spillway as millions of gallons of water thundered over the side of the dam wall.