An interesting experiment would be to mark a waypoint on structure in the DI view as soon as it appears at the right of the screen...(placing the cursor crosshairs at the point where the structure touches the bottom in the DI view)...

And immediately mark another waypoint by pressing "Mark"...(this would set a waypoint at the GPS antenna location)...

Then compare the 2 waypoints on the chart view zoomed all the way in...

Now ...add another experiment...

Mark a waypoint on structure in the DI view as soon as it appears at the right of the screen...(placing the cursor crosshairs at the very top of the structure up in the water column....

And immediately mark another waypoint by pressing "Mark"...(this would set a waypoint at the GPS antenna location)...

Then compare these 2 waypoints on the chart view zoomed all the way in...

Rickie