The Swift River originates near Kancamagus Pass in the White Mountain National Forest, flowing eastward for approximately 25.6 miles through Grafton and Carroll Counties before joining the Saco River in Conway. This freestone river descends over 2,400 feet through its course, creating a dynamic waterway that transitions from remote mountain headwaters to more accessible lower sections along the Kancamagus Highway (Route 112).

The upper reaches, beginning near Livermore in Grafton County, harbor native brook trout populations in cold, clear waters fed by mountain tributaries. These headwater sections require hiking to access and flow through pristine national forest lands. As the river progresses eastward into Carroll County, it gains volume and power, creating the whitewater sections that attract paddlers from across the region.

Paddling opportunities range dramatically across the river's length. The Bear Notch Road to Rocky Gorge section offers 4 miles of Class I-III water suitable for intermediate paddlers, with relatively forgiving conditions and scenic forest surroundings. Downstream, the Rocky Gorge to Lower Falls stretch intensifies to Class III-IV over 2.6 miles, demanding solid technical skills. The most challenging section, Lower Falls to Darby Field sign, presents Class IV(V) whitewater across 5.35 miles, featuring complex rapids, tight channels, and powerful hydraulics that test experienced kayakers.

The river's season typically runs from late April through October, with peak flows during spring snowmelt (May-June) providing the most exciting conditions. Summer offers more moderate flows, though water temperatures can rise significantly by late August, particularly in lower sections. Fall brings spectacular foliage viewing opportunities along the river corridor.

The Swift River watershed supports diverse wildlife including moose, white-tailed deer, black bears, and numerous bird species. The riparian zones feature mixed hardwood-conifer forests with paper birch, sugar maple, hemlock, and white pine. Native brook trout thrive in colder upper sections, while the lower river receives stocked rainbow and brown trout.

Rocky Gorge Scenic Area serves as a major landmark and access point, featuring a dramatic narrow gorge with cascading water accessible via short paved trails. Lower Falls provides another popular access point with parking facilities. The Albany Covered Bridge crosses the river approximately 2 miles downstream from Lower Falls, offering a historic landmark along the paddling route.

Access points concentrate along Route 112, with parking areas at Bear Notch Road, Rocky Gorge, and near Conway. The White Mountain National Forest requires parking passes at most trailheads. Swimming is prohibited at Rocky Gorge following a 1942 incident, though other sections allow swimming when conditions permit. Water levels fluctuate significantly with rainfall and seasonal patterns, requiring paddlers to assess conditions carefully before launching.