In "Book One: Water - Chapter 9: The Waterbending Scroll", Zuko and the pirates search for Aang and his friends by sailing a steamboat and the pirate ship up a river inland from a port. Later, when Aang and his friends escape from Zuko and the pirates and are fleeing from them, they sail down the same river and encounter a waterfall. How did Zuko and the pirates get the steamboat and the pirate ship up over that fall in the first place?