Wow that is pretty awesome.
They have to be careful what they say. Once you find a treasure, everyone else, from the local state, to the feds, to the UN, to foreign countries, will be demanding a piece of it (or more).
So you risk your neck, and your cash, and do the work, only in order to be required to hand it all over to some government agency, or else go to jail.
The result of this is that nobody will tell where they found anything or just exactly which ship it came from—and so history is the loser.