Here's the detail comparison showing what I was describing above:

Lowrance HDS7 Screenshot, last updated 2012:

The 6 foot and 9 foot soundings in the upper center of the Lowrance chart probably should correspond to the 69 and 97 foot soundings on the official chart. I can't imagine where the 5-foot sounding came from. The asterisks depicting rocks in the ship channel probably were put there by someone who interpreted the official NOAA chart's "rky' notations wrong.

Official NOAA raster chart showing same area:

Bottom line, if all you had was the Lowrance CP for navigation, you'd steer your sailboat clear of the main ship thoroughfare for Buzzards Bay for fear of running aground. This kind of stuff is why I bought the Navionics charts for my Lowrance CP as an add-on. It's also nice to be able to be able to download unlimited updates for $99/year and ba able to switch between different charts without running below to the paper or laptop version (but I do keep the NOAA charts updated and Coastal Explorer is usually running at the nav station laptop when we're out for more than a daysail).