use 455 to search the area, you can go back in 800 to get a closer look at your structure. I run 455 mainly. 30 fow + I go with the 800. In skinny water I would run the 455 to find the structure then mark it on the unit. then go back and fish it without running over it to keep from spooking the fish...just run toward it into the wind and watch your mark on the screen then stop in casting distance. hope it helps