ligan

In law, anything sunk in the sea, but tied to a support at the surface, as a cork or buoy, in order that it may be recovered. See flotsam and jetsam.

Goods sunk in the sea, with a buoy attached in order that they may be found again. See jetsam and flotsam.

goods (or wreckage) on the sea bed that is attached to a buoy so that it can be recovered