Been on the Cod at least 12 times. Started going when the museum was fully accessible. Since then, parts of the museum have been sealed off with plexigalss to allow you to see in, and some things like silverware have been stored for protection from theft I assume. Lots of hard work by volunteers make this an incredible experience. Visitors must enter and exit through the original hatchways and climb up and down ladders. Kids love this, although younger ones have to be encouraged. Small kids, older people, and physically challenged may find it too difficult.
Children love climbing through the museum and being directly in history rather than a book or video. The somewhat musty smell is to be expected, but it's worth a little historic odor to be able to take a walk through history.
Been to the U-505 in Chicago. While interesting, it's a long line, through a hole in the hull, and with a tour guide. It's worth a visit to the U-505 to compare US and German subs, but the USS Cod is much better, and an amazing treasure in Cleveland. A must see! (PS- the museum is down the street from the Rock-n-Roll Hall of Fame, toward the airport and has a small free parking area)