Downright scary! Could have been charting error. The NOAA chart, BTW, shows the position you cited as being right up against the shoreline obstructions E of the red/green mark, just as do your two chartplotters.
IMHO, chartplotters and GPS are not the proper aids to navigation for places as tight as this. The Mark I eyeball and, especially, radar are the tools of choice for this situation.
Glad you got off with nothing more than you did AND with an initiation to the Cruising Club of Maine :-)