Contour Mode may be turned "on". In a SI view, menu button once for SI express menu, down to SI Enhance, right to menu, down to contour mode, turn "off" if "on". 

When Contour Mode is turned on, the bottom is graphed at a constant point on the display, regardless of changes in depth. The Side ImagingŪ beams are divided by a vertical line. The water column is removed from the view, which allows the display to show targets at their linear horizontal distance. The location of a target may be easier to interpret when the water column is removed. (Off, On; Default = Off)
Mike