I have used the two wire version of this to locate pipes but have never tried it for underground bodies of water. To do it take 2 pieces of wire about 12″ long and bend them in an L shape. The short side of the L needs to be a little longer than the width of your hand. Hold the short end loosely, one in each hand, like you would a bat or shovel handle letting the tip of the wire rest on your pinky finger to keep it from slipping through your hand. Hold the wires out in front of you like you are carrying 2 mugs of beer. Make sure the long side of the L is pointing straight ahead. Begin walking. Remeber dont grip the wire, just let it rest in your hand. When you cross a water line the wires will start to turn inward towards each other. When they form a straight line parallel with your chest you are right over the water line. Mark the spot and then move over a few feet and repeat the process. When you cross the water line again mark that spot. Draw a line from yuour first mark to your second mark. That is the direction the pipe is going. When water moves through a pipe it creates static charge. The wires react with charge like a magnet and it causes them to move. That is how the wire method works.