Interesting thread. I recall, back when the earth was cooling, people would put a flashlight in a mason jar (probably after they emptied the contents) and filled it with rocks. Tied a cord on it and hung it off the side of the boat. Same prinicple. Had a friend that lived off the Hiwassee on one of the backwaters. He would turn on the dock light about an hour before dark. Really effective, especially during the willow fly hatch. People would bet as to what they would catch next.