One other possible option depending on compatibility with units is C-Map Contour+ charts(US & Canada Inland and Coastal). I've just had the chance to run these side by side with Navionics + on HDS units and at first glance and prefer the detail. More depth soundings across the board and very detailed contour lines with color shading if desired. These may be specific to and now included with HDS units so C-Map Discover or Reveal Charts may be another option for other Lowrance multi function displays.
