Flotsam: wreckage from a ship found floating on or washed up by the sea. People or things regarded as worthless.
Jetsam: material or goods that have been thrown overboard from a ship and washed ashore, especially material that has been discarded to lighten the vessel if a ship is endanger of sinking.
Lagan: goods thrown into the sea with a buoy attached so they may be found again.
Derelict: goods that have sunk to the ocean floor with no hopes of reclaiming.