If you're in Chicago, visit the Museum of Science and Industry. You can tour the U-505, the last vessel captured by the US Navy by a boarding party (in the Caribbean, in 1945).

If you're in Groton, Connecticut, you can (or rather, could -- I suppose you can still) visit the US Navy's flagship submarine training center. You can also visit USN Nautilus, the first atomic-powered boat (and the first under the North Pole). There are also surface ships to visit there, including a sail-powered whaler. When I was there the Dutch "tall ship" used for training was in port and we got to visit her, too.