I think as technology advances you'll see units with better bottom separation, although most units are a few inches at most now. This is why I love my side scan on the 899HD SI I've got on the console. I can mark big rock piles off to the side, set a waypoint then work my way around and get perfect lure placement. Big rocks and all those nooks and crannies are always going to be a pain. I just wanna know if there's fish on them, if I can get one to rise up and see it, the graph has done it's job.