The Suir rises on the Devil's Bit in Tipperary and runs a hundred and eighty-five kilometres south and then east to Waterford Harbour, where it joins the Barrow and the Nore. For most of its length it flows over Carboniferous limestone — turning to Old Red Sandstone toward Waterford — and that lime-rich water makes it one of the great brown-trout rivers of Europe, producing trout in numbers few rivers can match. It is a wide, strong, even-flowing river of clear water, weed-rich glides and defined pools through fertile farmland. The Suir is also a salmon river — it gave up the Irish rod record, a fish of fifty-seven pounds, in 1874 — though, as on so many Atlantic rivers, the stock has declined, the best of it lying downstream of Ardfinnan. The character is classic limestone water. Wading is steady over firm gravel and weed, the clear flow rewarding a careful approach.

Wading: Weed and clear water over firm gravel

EPA river-invertebrate monitoring on the Suir confirms mayflies, stoneflies, caddis, chironomids and other aquatic diptera, and freshwater crustaceans are present across its extensive monitored reaches - food-presence evidence only, with no record of hatch timing or emergence strength.