Water transport was critical long before the industrial era. Boats on rivers or barges on canals could carry great weight with relatively little effort, and sailing ships had long been used for global commerce. But while horses could tow a canal barge in any weather, a boat on a larger body of water, such as a river, lake, or ocean, usually needed wind to move, and wind was unreliable. Ships in the eighteenth century sometimes floated in harbors for days or even weeks waiting for enough wind to let them maneuver into open water.