Drive your boat in a grid pattern 50-100 feet away from the suspected structure (river bend, dam, hump). Set your Side Imaging range to 60 feet left/right. Cruise at 3-5 mph. Mark every piece of isolated cover (a single log, a rock pile) with a waypoint.
Once you have 10 waypoints, drive directly over the best ones. Switch to Down Imaging. Lower your speed to 1-2 mph. Confirm that the "blips" on Side Imaging are actually fish (white ovals) and not just branches. catfish finder