Flotsam: lost because of wreckage
Flotsam is wreckage or cargo found floating after a maritime accident. The defining idea is that it was lost through disaster rather than deliberately discarded.
In the series, that distinction becomes a Gothic question: if the sea carries something back after a wreck, is it being returned—or presented?
Jetsam: deliberately cast overboard
Jetsam is property intentionally thrown from a vessel, traditionally to save the ship or lighten its load. Someone made the decision to sacrifice it.
That makes jetsam emotionally different from flotsam. It was not merely lost. It was chosen for abandonment, and the choice leaves a debt.
Lagan: sunk and marked for recovery
Lagan refers to goods sunk beneath the water but attached to a buoy or another marker so the owner can return. The intention to recover them remains.
For a romance series, that marker is irresistible: it is both a claim of ownership and a promise to come back. The water has time to decide what that promise means.
Derelict: wholly abandoned
Derelict property has been deserted at sea without hope or intention of recovery. Of the four terms, it represents the most complete surrender.
The final category asks the darkest question in the sequence: what happens when something abandoned beyond rescue continues waiting anyway?