Sail 5 Essence 4?
Wherever there is water the ship will sail, the bottom of the keel barely breaking the surface. It can travel far inland up the shallowest rivers or chart unnavigable shoals and reefs. It can only be stopped by a point where it's weight would rest on land like an exposed sandbar or a narrow stream. Fords of sufficiently wide rivers are no impediment as a long as there is at least an inch of water. Neither will currents stop it or change it's course.
