It was my first time entering the snug inner harbor on the deserted island with the abandoned community of Oderin.
It was low tide. We were approaching the harbor entrance slowly, at less than one knot, with the centerboard down (10.5' draft), but unlocked.
We had passed the last of three buoys marking shoals and rocks in the entrance.
I had drawn my route (blue line) on the chart using the most detailed chart that I had. It wasn't a large-scale harbor chart, and I had OverZoomed in to draw the route.
As we approached, I could see that the plot was off, and I needed to keep somewhat farther south (to starboard) as we rounded the rock. But I had more faith in the accuracy of the chart than was justified, and the centerboard grounded on a tongue extending from the rock in the picture.
A low speed grounding in good weather with the centerboard unlocked is not a problem in Issuma, we merely needed to raise the centerboard, reverse away, and then alter course to continue.
I made a satellite image chart (using the OpenCPN VFkaps plugin, https://www.venturefarther.com ) of the entrance to the harbor, which was a larger scale, and more accurate. It showed it was shallow where we grounded, but it wasn't the chart I was using at the time.
If I didn't have a chartplotter, I would have steered farther away from the rock (in the picture) on the inside of the bend, because the water is almost always shallower on the inside of a bend than on the outside. But I was overly trusting to a chart that was not a large-enough scale to justify following it.
Anyway, no harm done, just a reminder of why one wants to approach an unfamiliar port slowly.
Grounding on the entrance to an unfamiliar port with the centerboard down wasn't all that unexpected.
The surprise came later, after my second visit.
I spent over a week anchored in the inner harbor, making a video (coming soon).
Rounding that rock in the other direction, as I left the inner harbor and headed back to sea was when I was surprised--
ALL THREE BUOYS WERE MISSING!
The buoys had been taken away for maintenance. I had my chartplotter tracks that I had used before to follow (avoiding the part where I ran agound), so it was no problem to leave without any buoys. It was just amusing.