There are many waterfalls to choose from to use as locations. Please note that when filming at popular tourist places, the locations can not be closed off so it interferes with regular tourist operations.
Rivers com in all shapes and sizes and most of them have some kind of a waterfall in them.
The South Coast of Iceland has many pearls of nature one can visit and enjoy. Seljalandsfoss waterfall, Skogafoss Waterfall, Solheimajokull Glacier, Reynisfjara Black Beach and the village of Vik are the most popular places to visit and fit all nicely in an excursion from Reykjavik in a day. You get a close view of Iceland; waterfalls, glacier and the coast of the North Atlantic Ocean.
The Golden Circle is the most popular tourist excursion in Iceland. On this tour one will visit the Thingvellir national park, Geysir Hot spring area and Gullfoss waterfall. Optional are visits to the Faxi waterfall and Kerid volcanic crater.