There seems to be an instinct to throw change in the water. On a recent trip through a tourist coal mine (Ashland, Pa.), there was a pool of water in a side shaft. No sign indicating that you were expected to throw coins in, but people had done it (also a few dollar bills). Then on a pedestrian bridge over the Niagara River just above the falls (Goat Island), I could see lots of coins on the rock bottom. No, I didn't try to get them The edge of the falls was less than 100 yards away.