The riverbed rocks and the associated rapids made the gorge valley an infamous passage for shipping, even for the most seasoned boatmen. During the period of the Ottoman rule, the ships were guided through by the local navigators, familiar with the routes, called "kalauz" (from Turkish "kalavuz", meaning guide, travel leader). During the rule of prince Miloš Obrenović, local Serbs gradually took over from the Ottomans, being officially appointed by the prince. In order not to aggravate the Ottomans further, the prince named Serbian navigators by a Turkish name, "dumendžibaša", from "dümen" (rudder) and "baş" (head, chief, master). The navigation fee was divided among "dumendžibaša", "loc" (river pilots) and regional municipalities.