The Keswick River is a narrow, meandering tributary of the Saint John River (Wolastoq) in York County, New Brunswick. It originates in the wooded hills north of Crabbe Mountain and winds through farmland near Burtts Corner before joining the Saint John roughly one kilometre past the Route 105 bridge. The river doubles back on itself repeatedly, meaning distances on the water are roughly twice the straight-line distance along the road.

The overall character is gentle and flat, with no rapids or portages. The current is slow throughout, and the river curves constantly through farmer's fields with eroded clay banks on the outside of bends and small gravel beaches on the inside. Layers of clay exposed by erosion are visible along the higher banks, and bank swallow colonies nest in the steeper cliffs. Bald eagles and fish in deeper pools have also been observed along the route.

The primary hazards are minor strainers, occasional deadfall, two notable submerged logs (deadheads), and at least one log jam that must be navigated around. Fallen trees tend to collect on the outside of turns, so keeping to the inside of bends is advisable. The river is best suited to early spring when water levels are high enough to float through the many tight bends without grounding. In summer, water levels drop significantly and paddlers may need to walk sections; the lowest stretch from the Route 105 bridge to the Saint John River remains accessible throughout most of the paddling season except during drought.

Several distinct sections are commonly paddled. The Tripp Settlement to Route 104 route near Burtts Corner covers approximately 7.6 kilometres and is rated easy. The full lower Keswick River, running from the Upper Stone Ridge Road bridge to the Route 105 bridge, can take up to eight hours and is typically tackled in sections. From the Route 105 bridge, paddlers can continue approximately one kilometre to where the Keswick meets the Saint John, with the option to paddle around nearby islands.

Access points are located at road bridges. At the Tripp Settlement Road bridge, parking is available in a small pulloff and a path leads down to a gravel beach beneath the span. At the Route 105 bridge near Keswick Ridge, a gravel road leads to a boat launch under the bridge. Paddlers should avoid blocking the access road at the lower take-out.