I fished a lake earlier this year that gets to be close to 20', but we were catching big bass in under 6'. we were catching them in and around a weed line, probably 6" to 1' above the weeds, about 2' off bottom, when were on a less weedy spot. I guess I'm saying deeper water is not always a sure bet...if you know the lake well, try a spot that produced for you in the open season. If you know where any weed lines or bottom irregularities (drops,humps, ledges, etc.) are, that might be a good bet.