On pulling into the Chesapeake, we were passed on the left by a surprising vessel. A submarine cruising on the surface. See the picture.

We also noticed that we had run out of chips for our plotter. This meant we could no longer easily track our exact location on the plotter. We were very happy with Rich's advice to bring paper maps with us, which we now relied on. In order to get a good fix on our location, we now had to look up our GPS location on the map by hand. Maybe this doesn't sound like much a difference, but it has a significant impact on navigation, especially when getting into confined spaces, which we were about to do in the Potomac.