Flotsam & jetsam are debris found floating in an ocean, sea, or lake that originally comes from a sea vessel. Flotsam has been lost from a ship unintentionally while jetsam has been intentionally cast from a ship to lighten the load. Flotsam and jetsam are used in worldbuilding as a resource in water worlds or as a location where shipwreck survivors may be found clinging. It may contain shipping containers, barrels, rope, and other elements. Illegal goods or people may have been tossed overboard to avoid being found by the authorities. Shipwreck towns and raft towns may be made from flotsam and jetsam.

Flotsam and jetsam may contain clues about the fate of a vessel.