So you want to know how to buy gold coins from treasure ships that sunk? The answer to that question is rather easy. The most important of which is that you gotta have the money. With money you can buy the whole ship, salvage it or if you really got a lot then you can buy the area of sea bed where it sunk and stick your "No Trespassing!" post somewhere around it.
But really, you can. But the real question is if it's really a good idea to buy gold coins from sunken treasure ship compared to buying gold coins fresh off the mint.
How much would you buy or sell gold coins that was salvaged from the Black Pearl? With the money you put out to buy it, you probably could have gotten yourself maybe 3 or 4 pieces salvaged from the Thousand Sunny. I'm afraid i might have used a bad analogy here (it's Captain Jack Sparrow's sheep we're talking about here) but take any semi-famous ship, and take the coin out of it and the hype of finding the long lost ship of lollipop hype would inflate the value of the gold coin that it won't sink.
Then just wait after the hype dies down and people forgot about the indiana-jones dicovery of this sunken ship and you're left with a gold coin no different from a gold coin minted yesterday. Then you'll realize that you can no longer sell this gold coin at the price you can break even.
Okay then, maybe you'll say "It's a collectors item, there's only a few of these around", but then they already found one ship, and then they found the Ship Anti-Lollipop which Ship Lollipop cannoned down dragged by the undercurrent a few kilometers off the original spot carrying the same types of coins, and a fleet of them a few kilometers farther (..apparently, Ship Lollipop was a Juggernaut of a ship that brought the whole candy fleet)
Then your coin's no longer special.
Salt water and metals don't mix. Though gold is a bit resilient unlike bronze and solver coins still, the quality of the gold coin could have degraded in it's years soaked in salt water. It adds to the authenticity of it being from a sunken ship, but would you really care to trade quality over an authenticity certificate?
You should appraise the coin by it's own merit and not by it's 'status'. Look at the coin, look at the quality and it's grade. If it has my image on it, then go for it! If not, then examine it more carefully. And if you really know that it's a good purchase then by all means.
Goodluck!
