You Decide What's Fair 1. Most nationalistic themed movies need a baddie. In this case it's the U. S. while the good guy is Spain; where the script originated.
2. Maritime salvage & "finders" laws vary by country & time period. So let's make it simple.
3. Spain was taking money, perhaps gotten unethically or not legally, from the U. S. to Spain 100s of years ago when the ship sank perhaps by conflict. Spain has made no active effort to retrieve the lost treasure so may have given up the possible right of ownership.
4. Ship, forgotten & abandoned, is discovered by a person, portrayed as a greedy American, who risks his life; his time; his money to search & find the lost-at-sea treasure. By salvage law he is entitled to compensation relative to value. By finders law he is rightfully the new owner.
5. Your decision?