I have stumbled across a question that I didn't even know was an issue. Should the bottom of a narrowboat be painted? I've been doing some reading about this and it does seem there are (surprise, surprise) two opposing camps on the matter.
It seems many aren't painted. It is believed that as the base plate of a narrowboat never sees the light of day, it won't rust. There isn't sufficient oxygen in the water for rust to form - according to the "no need to paint the bottom" camp. There are comments of people with 20+ year old boats with bottoms as good as new, so they claim.
Then there is the other side of the story - those that are determined you should paint the bottom of the boat.
I do recall reading something a couple of years ago that said boats in marinas are more prone to pitting of the hull than those on inline moorings or cruising.
Would like to hear your thoughts.