Socialist Federal Republic of Yugoslavia
Regarding rivers, the Danube was navigable throughout its entire course in Yugoslavia, linking the ports of Belgrade, Novi Sad, and Vukovar with Central Europe and the Black sea. Long stretches of rivers Sava, Drava and Tisza were also navigable.
Chain boat navigation
Due to the strong current on the Danube, chain boats could not use the chain when travelling downstream. They therefore had to have large paddle wheels on their sides, as additional means of propulsion, generating .