I know this is an old thread but I've done some detecting recently at the swimming area of our local reservoir in NE Kansas. The lake level is down over 6 feet which exposed the entire swimming area cove. I found lots of dimes and pennies, fishing weights and pull tabs but no jewelry. Seemed really odd walking around an area where a couple of years ago I was swimming in head-deep water. Might be something to check at your local lake.