When a sovereign military vessel sinks, it does not become finders-keepers territory for deep-sea treasure hunters. Under international customary law and domestic statutes like the U. S.
Sunken Military Craft Act (SMCA) of 2004, sunken warships remain the permanent property of their flag state indefinitely, regardless of location or age. Sovereign immunity guarantees that military vessels retain their status even after sinking. This principle was famously tested in 2007 when Odyssey Marine Exploration discovered the wreck of the 1804 Spanish frigate Nuestra Senora de las Mercedes off the coast of Portugal, recovering over $500 million in silver and gold coins.
Spain successfully sued in U. S. federal court, arguing that the vessel was protected by sovereign immunity.
The court ruled in Spain's favor, ordering the salvage firm to return the entire cargo. The SMCA strictly prohibits unauthorized disturbance, excavation, or recovery of sunken military craft. Beyond property rights, these wrecks often serve as war graves and contain unexploded ordnance, hazardous materials, or sensitive technology.
Consequently, salvage law rules that reward finders do not apply to sovereign warships unless explicit relinquishment occurs.