Three years ago when we visited New London, we were able to see the Submarine Museum but the Nautilus was closed. This year, we would have been able to see the Nautilus but I made the mistake of taking us there on a Monday when the entire museum was closed.
We made up for my error by going to visit the nearby World War II National Submarine Memorial.
This small park is dedicated to the 52 submarines lost along with 3600 submariners during World War II. Enlarge that picture on the bottom right and you will discover that the first submarine lost during WWII was the Sealion and that it occurred on Dec 10, 1941, just three days after the attack on Pearl Harbor. The story of that loss can be found here.
While in New London, we also sought out the tallest lighthouse in Connecticut. It is not open to the public, but can be found along a road in a residential area.