Crossword clue: goods sunk in the sea, with a buoy attached in order that they may be found again. see jetsam and flotsam. blackstone.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
goods (or wreckage) on the sea bed that is attached to a buoy so that it can be recovered