40 years ago, I lived on a narrowboat that had portholes.
It was dark enough inside at the best of time, but you could guarantee that several times a day, it would suddenly go a whole lot darker as some nosey parker pressed their face up against one of them to have a good old nosey.
In fact, it wasn't unknown for faces to appear simultaneously at several portholes when an entire family wanted a peek.
I have to admit that I soon lost my patience, and was not always very polite to them. 
On the other hand, people who stopped to chat to us and showed an interest were usually invited in to have a look. This was back in the days when living on a boat was quite unusual.