All boats, at some stage, will have water inside the hull either from leaks or condensation. Obviously, the first thing you is minimize these leaks or reduce the cause of the condensation. The second thing you do is prevent this water from pooling and soaking woodwork, upholstery etc.
The forward Engine Room bulkhead on TIH has always had some water damage / wet rot. I was happily ignoring it as I assumed that the whole bulkhead was compromised and it would be a major job. I finally bit the bullet and happily found that only the bottom edge was affected.
Some penetrating epoxy and fill the void with epoxied marine ply and it should be good to go.