Devblog 30: Cargo Boats and coastal supply routes
Siege Camp's September 11 announcement brings the Cargo Boat back with two rowing positions. Rowers control forward and reverse movement, while the helmsman steers and the sails use the wind. Coordinating those jobs becomes part of transporting a crew and its supplies.
Prepare the port as well as the boat
The 
Shipyard constructs large vessels at coastal towns. Homestead Ship Docks provide secure storage and become necessary for repairs. A docked ship can still be damaged or disabled. Elsewhere, Canal Walls carry water through defenses, connected Aqueducts receive decay protection, and larger vehicle stockpiles encourage bulk transport instead of overloaded personal inventories.