[jimtorr]

I believe that the principle of national ownership is that the vessel must be continuously gaurded by Spain in order for Spain to retain ownership.

That is why they do not dispute ownership of all the dozens of treasure ships that sank around the world. They only claim ownership of what was sunk near Spanish waters.

[pierrem15]

But Spain does dispute ownership when the wrecks are found with treasure and wins their cases (Portuguese waters):

https://www.cnn.com/2012/02/01/world/europe/spain-u-s--treasure-dispute/index.html

There are some Florida ones also I believe.