The River Plym rises on Dartmoor in Devon, England, flowing southwest to meet the River Meavy before continuing south toward Plymouth Sound. The city of Plymouth itself takes its name from this river, which tumbles through a landscape of rocks, pools, and waterfalls carved from the Dartmoor terrain.

The river is well regarded among paddlers, with the upper section from Cadover Bridge to Shaugh Bridge considered the most technically demanding stretch. The British Canoe Union has described this section as the hardest part of the river to navigate, featuring pool drops that are not recommended for novices. It has been characterized as one of the best Grade 5 runs in England. The lower sections from Shaugh Bridge to Bickleigh Bridge are more forgiving past the first rapid, provided water levels are adequate.

Water levels are closely tied to rainfall. The Plym is typically one of the first rivers to rise during heavy rain and one of the first to drop afterward, making timing critical. Experienced paddlers monitor weather conditions carefully before committing to a run, particularly on the upper section. Combining a Plym run with the Upper Dart and River Erme is noted as a way to put together a full day of high-quality paddling in the region.

The river passes through varied Dartmoor scenery, with historic bridges and woodland adding character to the corridor. The Plym Valley Railway runs alongside a section of the river. The waterway also supports brown trout, sea trout, and salmon, with angling managed largely by the Plymouth and District Freshwater Angling Association across both upper and lower reaches. Paddlers should be aware of the presence of anglers, particularly on the lower sections.