Very good advice all through, and don't underestimate the "damp" smell. A boat may be wet inside, but it shouldn't be generally damp. That is just a recipe for rot, and almost no matter how hard you look, you may miss it.

I had a full very professional survey done on the boat I bough last Sept, and we did find some rot, which we have now dealt with, we also didn't find some serious rot in a deck beam and carlins, which we are now dealing with. This has kept a boat builder busy for 6 months full time, and even then, I am working every spare moment I have as well. (And no I still don't regret buying the boat!)