Jetsam means goods that, after being abandoned at sea, sink and remain underwater. This applies to cargo or equipment thrown overboard from a ship in distress and either sunk or washed ashore.
This is also termed as jettison. The jettison must be made for sufficient cause and not from groundless timidity. It must be made in a case of extremity, when the ship is in danger of perishing by the fury of a storm, is laboring upon rocks or shallows, or is closely pursued by pirates or enemies. If the remainder of the cargo be restored by such sacrifice, the property restored is bound to pay a proportion of the loss. In ascertaining such average loss, the goods lost and saved are both to be valued at the price they would have brought at the place of delivery on the ship's arrival there, freight, duties and other charges being deducted.