Alright captains, skippers, pilots, pirates, helmsmen, etc, a water based vehicle question for you!

A good friend is looking at buying a used grp hull boat.

He has narrowed it down to a few options; however, both boats have not been removed from their fresh water moorings for a reasonably long period of time (one having spent the last six years in fresh water and the second, closer to nine, albeit it is currently out in dry dock).

My knowledge of boats is limited but I was always under the impression that a boat should be taken out of the water every 12-24 months to have the hull cleaned and a sacrificial antifouling paint applied? By not doing so, you run the risk of hull damage, osmosis, and general degradation. The longer the boat is in the water for, the greater the risk, because the hull doesn't have the opportunity to dry out.

Both boats have been kept on private moorings, hence not being removed, even for winters. One is a private sale and the other is with a broker, hence it now being out of the water. The broker is nonplussed that the boat was in the water for circa nine years and said a 'hull inspection' should allay any concerns.

This came up in a chat over the weekend, with said friend, and I was less convinced that a survey would be able to ascertain the full extent of any damage caused - my assumption being that it is non-invasive and therefore they will moisture test the hull, look for signs of osmosis and do a visual check; however, this isn't going to show internal damage to the layers of grp, is it?

Views and opinions of those far more knowledgeable in this area welcome! Is the non-removal from the water a 'walk away' or something that can be navigated around with a good inspection?