This is a deep lake, but most of the docks I've been scanning have been in 15-30 feet of water I'd guess. I did switch back to 455 Khz yesterday and was able to start seeing the dock floats and boat lifts at least. I didn't mark anything that I presumed to be crappie under the docks, but it was a really windy day and I didn't make a very concerted effort at it. I may head to a lake next week that has a MUCH healthier crappie population, just so I can spend some time staring at side scan and figuring it all out. For what it's worth, I did scan at 40-50 feet almost all the time. Occasionally if I was in really deep water I'd switch to 60 feet, but that was the upper limit and that was rare.