Look at the SS Central America case law.
The way I look at it personally, an Admiralty Arrest on a shipwreck, is a misuse of the foundation of why this was created, to provide a means of assistance to ships in peril that were sinking, for other ships to help the vessel survive, but more to help the crew survive. It provided an incentive for other ships to respond to one in peril.
For a shipwreck on the bottom, there is no peril associated with this, that another ship has to respond to rescue the crew nor the vessel. The only peril is the sea state and financial in the recovery associated with on the bottom. That was not the intent of the Law.
The foundation of Admiralty Arrest, the ability to assist the crew or the vessel, with a shipwreck on the bottom and the peril involved in the assistance has long gone.
Law of Finds. This is far more applicable, but again, misused on shipwrecks. The cargo is not floating around, nor washed up on shore. It is set on the bottom. If the wreck has been abandoned, or fully paid off by insurance, then the owner certainly has given up the right to procure salvage. In the case of an Insurance payoff, this means that ownership has transferred to the insurance company.
A wreck sitting on the bottom, is a fixed asset, not flotsam and jetsam. and the owner has the right to refuse and/or pay for a recovery. Just because you find it, it is not the Law of
Finds as defined by the provisions/definitions of the law.
There is a big difference between a finders fee and the Law of Finds.
It is far past the time for salvors looking at historic shipwreck recovery, to find a different legal avenue to protect, secure, and recover their find.
It would be best for all sides to come to a consensus, and balance the archeological with the profit. Else, there will be illicit recovery, with no archeological context, which diminishes the value of the artefacts, and adds nothing to historical archaeology.
Afterall, if that coin could not be dated, or have some sort of archaeological provenance, it simply becomes another piece of spot price gold, just like the fakes.
ie an silver coin is worth $60, but with an Atocha cert, is worth $200..