Wouldn’t it make sense to have a survey done before a sailboat is put up for sale ?
That would mean the owner pays for the survey, and gets to pick their own surveyor, and since the surveyor is working for them its not necessarily to the benefit of the buyer. If the buyer pays for the survey, they get someone working for them to identify everything that's wrong.
That said, it really is up to the buyer to have sufficient knowledge to do a walk through of a boat and do a rough determination of value and condition in order to make an offer to the seller - contingent on the survey. I kind of do think this is backward - I really would like to know everything about a boat before I make an offer. But you do get to negotiate on anything the surveyor finds, so the offer accepted is often just a starting point. But the seller does kind of have you in a bit of a bind if you've already spent almost $1,000 on a survey, and may refuse to negotiate if they can claim "of course the hatches leak, that's wear and tear on a boat this age".
That's why I'm an advocate of buyer's brokers. If you get a good one, they'll be more than capable of giving a boat a good once-over and spotting things that you might not, and that can help you decide whether to make an offer and invest in the survey. That costs you $0.