[gamblor956]

This.

Shipwrecks are governed by maritime salvage law, an international set of legal conventions governing the recovery of vessels and properties aboard them.

In a nutshell, the putative owner of the vessel or the properties recovered from it has two years from the end of salvage operations to lay claim to the vessel/goods recovered. If the salvage was not performed under contract, then they must pay fair value for the salvage services, but the sources I found are all over the board on what "fair value" is in that context.