Pay for what you get
"This allowed me to get the boat well under the asking price and also made sure I knew what I was getting myself into."
Besides the obvious benefits of preventing you buying a pup, the ability to pay for what you're really getting as opposed to what the seller would want you to believe you're getting is very useful. Even small deviations from the stated condition can result in meaningfull reductions in the selling price.
You could possibly save at least the value of the survey and get peace of mind for free.