Lough Derg is the largest lake on the River Shannon, Ireland's longest river, stretching approximately 37 kilometres in a direct line from the town of Portumna in the north to the twin towns of Killaloe and Ballina at its southern end. The lake borders three counties — Clare, Galway, and Tipperary — and offers around 160 kilometres of shoreline for experienced paddlers to explore, with the full perimeter of one coastline extending to roughly 60 kilometres. There are 14 formal access points distributed around the lake, including a Waterways Ireland marina in Scarriff and access at Mountshannon, Killaloe/Ballina, Portroe, Ogonnelloe, Whitegate, Garrykennedy, and Kilgarvan Quay on the northeast shore, among others.

The lake accommodates kayaking, canoeing, and stand-up paddleboarding. The most direct north-to-south route of around 37 kilometres can be completed in a single day under favourable conditions, though a multi-day touring approach allows for exploration of the lake's numerous coves, bays, and islands. One well-documented route runs from Scarriff Harbour to Holy Island pier, approximately 7.5 kilometres each way. The initial section follows a narrow river channel that provides some shelter from wind, though paddlers should be aware that this stretch is also used by motor cruisers, and the return upstream journey can be more demanding due to river flow.

Wind is a significant factor on Lough Derg given its size and open character. The lake's exposed stretches require paddlers to exercise appropriate judgment, and the sheltered river sections near Scarriff are noted as preferable during periods of poor weather. Wild camping along the shoreline is possible in remote areas, though there is no explicit legal framework permitting it in Ireland, and a leave-no-trace approach is strongly advised.

Wildlife around the lake includes white-tailed sea eagles, swans, and leaping trout. Holy Island, accessible from Mountshannon or Scarriff, is a historically significant site and a popular paddling destination. The lake has over 90 heritage sites in its broader area. Guided tours and equipment rental are available through operators including Lough Derg Watersports at Kilgarvan Quay and ULAC Adventure Centre, with Blue Flag beaches at Mountshannon, Portumna, and Twomilegate providing additional amenities for paddlers.