I believe I turned the speed off on the unit in the overlay settings. I wanted as little info as possible on the screen. I was just cruising along with the boat in gear. I would say i was going roughly 2 mph with my chart speed set to "fast" At first all i seen was just a column with my downscan so I then decided to do a little more searching in the area and thats when i found the bridge and decided to then go back and do a sidescan to see what it would look like. I actually had the coordinates of this bridge from the Lake Hartwell map plugged into my unit weeks ago and found some of the columns, but did not find that structure until yesterday.