The InkTide Vessel

Every sailor who crossed five thousand miles of the black water earned a swallow inked into his skin. Every sailor who never came back had one cut into the hull instead. A debt the vessel carried in his place, a soul it was obliged to ferry. The marked ships were said to hold what the Bonetide refused to give up. When a hull filled with swallows the crew burned it to the waterline and laid a new keel before dawn. The ones that were not burned were run up onto the shore for Vorukai to count.

Each layer is laid down as a line, the way a needle lays down a line. The strata do not bury the mark. They are the mark.