I couple I know used to run a charter
operation out of Great Oak. It's on Fairlee Creek. The entrance is at approximately 39° 16.060'N 76° 12.351'W. I don't think you'll want to be following waypoints going in. The channel is pretty narrow and you'll need to be paying attention to boat-handling, not the GPS screen
Getting in the entrance during an ebb tide is the interesting challenge. As you can see from the NOAA chart snip, below, you have to make a sharp turn to starboard to enter the creek. The channel is narrow and the tidal currents will do strange things to the boat as the turn is attempted. I've watched some boat drivers panic as their bow was suddenly wrenched toward the sand spit, just feet from the active channel.
However, with a little fore-thought and a cool hand on the wheel
(or tiller), it's very doable.