A suggestion. Say your tooling down the lake looking at SI. You see something that looks different on the image. Hit the cursor to freeze the image. Move the cursor over the item and hit the Mark key. Now you have a waypoint at that location. Change your view to Chart/Sonar view. On the sonar side of the view, hit menu once for X-Press menu. Go to Upper Range and set it to 10 feet above the bottom. Go to Lower Range and set it to 5 feet below the bottom. Navigate to the waypoint and scan the area in 2D sonar. If your using 200kHz, you will be looking at the bottom area equal to 1/3rd the depth. If using 83kHz, that will equal the depth. If anything is there, you should be able to see it.
Mike