Nod's waterways are older than most of its streets. Canals, flooded underpasses, underground rivers, and the brackish channels beneath the Stilts form a secondary transit network that is faster than surface travel for anyone willing to share the water with Merrow and worse.
The Ferrymen operate this network. They are boatmen, barge-pilots, and guides who know the safe channels, the tidal patterns, the passages where Merrow are fed enough to leave traffic alone, and the routes that should not be taken after certain hours regardless of how much the passenger is willing to pay. Most Ferrymen are Theriae with aquatic lineage or humans who have been in the trade long enough to develop an instinct for the water's moods.
The Ferrymen are not a formal organization so much as a professional community bound by shared knowledge and mutual survival. They charge for passage, don't ask questions about cargo, and maintain a strict neutrality in factional disputes.