We sailed through the Kanmon Straits or the Straits of Shimonoseki. It is the stretch of water separating Honshu and Kyushu, two of Japan’s four main islands. It is a very narrow passage with lots of commercial shipping as well as cruise ships and small fishing boats and everything in between. It was the original site for the second atomic bomb during WWII, but it was cloudy that day so the USA went with Plan B and bombed Nagasaki instead. In addition to being a strategic transportation center, it was the site of a ship building plant that is still in operation today.
So many vessels in these waters: a fancy French cruise ship, sharing the water with a commercial vessel and a cruise ship, the Pilot Boat, an odd-looking ship that might be a dredger, and a car carrier that can hold 3,000 cars.
To help ships navigating the Kanmon Straits, there is a sign on the shore that lights up with information about the tidal current: E or W (east or west), an up or down arrow, and a number for the number of knots. We were W down arrow, 1 going into the straits and looking back it was E, up arrow, 0 going the other way.