Fernhook Falls sits on the Deep River within Mount Frankland South National Park, roughly 40 kilometres north of Walpole in Western Australia's Great Southern region.

The falls are a series of cascades tumbling over broad granite boulders, and their character shifts dramatically with the seasons.

In winter, heavy flows send the river crashing over the rocks in a roaring torrent, churning the water into thick rafts of creamy foam — a result of natural tannins and saponins leached from the almost entirely forested catchment, which gives the Deep River some of the purest water in southwestern Australia.

Come summer, the flow eases and Rowell's Pool below the falls becomes a calm, inviting swimming hole. The surrounding forest puts on a wildflower display in spring, with hovea, flame peas, and orchids among the blooms.

The site also serves as a bush camping and picnic spot, and a canoe launch point for paddling the Deep River.