I believed that flotsam and jetsam were simply beach debris, but when I looked it up, I learned this: flotsam is floating wreckage of a ship or its cargo. Jetsam is part of a ship, its equipment, or its cargo that is purposely cast overboard, jettisoned to lighten the load in time of distress and is washed ashore. so if you are jetsam . . . Lagan (also called ligan is goods or wreckage that is lying on the bottom of the ocean, sometimes marked by a buoy, which can be reclaimed. Derelict is cargo that is also on the bottom of the ocean, but which no one has any hope of reclaiming (in other maritime contexts, derelict may also refer to a drifting abandoned ship). so according to this, only jetsam is washed to shore. I wonder if pondscum also has categories.