In 2008, Rok Rozman was competing at the Summer Olympics. Now he is an activist who has kayaked across six countries to help defend rivers against dams.

The Balkans is one of the last parts of Europe which has free-flowing rivers so Rok has helped set up the Balkan River Defence. This connects river conservation groups across Europe.

Slovenian Environment Minister Marko Maver said hydropower provided "one of the largest potentials for Slovenia moving to a low carbon future".

Video produced by Daniel South.

Photo credit: Matic Oblak

Footage provided by The Undamaged documentary film

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