mediumaevum:

The jus naufragii (right of shipwreck), sometimes lex naufragii (law of shipwreck), was a medieval custom (never actually a law) which allowed the inhabitants or lord of a territory to seize all that washed ashore from the wreck of a ship along its coast. This applied, originally, to all the cargo of the ship, the wreckage itself, and even any passengers who came ashore, who were thus converted into slaves. This latter custom disappeared before the jus naufragii came to the attention of lawmakers.