The Ballynahinch River is the short, wide, deep tail of one of Connemara's largest catchments — sixty-eight square miles of interconnected loughs and short connecting streams draining off the Twelve Bens through Lough Inagh and the Owenmore to the sea at Bertraghboy Bay. The named river itself runs only about four kilometres, beneath the castle, but it carries eight salmon beats and four sea-trout pools over a bed of Connemara granite, the water peat-tinged and quick to rise off the bog. This is classic western migratory water: grilse push in on the late-June floods, traditionally large for Ireland at six or seven pounds, and the sea trout — once the glory of the system — have recovered strongly since the estuary salmon farm was reduced. The granite-and-peat country gives soft, acidic water. Wading is steady on firm gravel and rock, with the usual care where the river runs deep and strong below the castle.

Wading: Deep, strong water below the castle