Just stumbled on this on YouTube. It’s a film dating from 1923 showing the wine boats of the Douro bringing the wine down river to Porto. This rabelos would have been navigating a river that had fast-flowing rapids, and it would have required skill and courage to do the journey. These days the Douro is dammed, and is altogether more sedate, and less wild.
Pathe also have a film from the Douro harvest of 1953, which is still of interest despite the cheesy commentary.
See also: historical pictures from the Douro