I would consider myself a beginner when it comes to detailed knowledge with this unit. I have owned it for a year. I am having problems with the unit when I get deeper than 1,500'. I would like to just see the top 400' or 500' but the unit goes "crazy" as I call it. The water depth changes sporatically with inacurate readings. At this point, I'm not wanting to see the bottom but rather bait balls or large pelagics. I have tried to manually set the water depth to 600' but this doesn't seem to resolve my issue. Any help is greatly appreciated.