Some surveyors acquire their knowledge from having been in some part of the marine industry , such as ship yard work, while others are Shipwrights. Still others attend a school such as Chapman's School of Seamanship in Stuart Florida. The California Maritime Academy, a four year California state college, located in Vallejo has many graduates that become surveyors. The laws of California that govern the purchase and sale of boats through a broker do not require that a boat be surveyed. However, all marine insurance companies that I am aware of require a survey before the boat is insured.
All marinas require the boats moored there to be insured.
All finance companies require insurance on the boats they finance to protect your investment and theirs. The infamous blisters reside where only an out of the water inspection of the hull can disclose their existence. Under the layers of paint in a well-maintained boat there may be chunks of corrosion detectable only by the trained and experienced eye of a surveyor. Even though many experienced boaters have been around boats most of their lives, they would no more be their own surveyor than be their own attorney. They may be reasonably good mechanics and good electricians.