[grobdriver]

Wouldn't sunken treasure be considered "Salvage" since the crew did abandon the vessel - perhaps involuntarily.
Salvage rights are routinely awarded.
Why else would someone go to the risk, trouble and expense of locating and raising a wreck or its cargo only to have the supposed "original" owner make a claim on it?
Leave it on the ocean floor, in that case!

[Quilla]

I understand salvage rights are awarded to the first to discover the ship. I could be wrong as is often the case.