The following information was published by the National Ocean Service:
You may have heard of “flotsam and jetsam” from the movies, but do you know the meaning of the words? While the phrase “flotsam and jetsam” is often used to describe “odds and ends,” each word has a specific meaning under maritime law.
Flotsam and jetsam are terms that describe two types of marine debris associated with vessels. Flotsam is defined as debris in the water that was not deliberately thrown overboard, often as a result from a shipwreck or accident. Jetsam describes debris that was deliberately thrown overboard by a crew of a ship in distress, most often to lighten the ship’s load. The word flotsam derives from the French word floter, to float. Jetsam is a shortened word for jettison.
Under maritime law the distinction is important. Flotsam may be claimed by the original owner, whereas jetsam may be claimed as property of whoever discovers it. If the jetsam is valuable, the discoverer may collect proceeds received though the sale of the salvaged objects.