Kootenay Lake stretches more than 100 kilometres northeast of Nelson into the heart of the Selkirks. The west arm — the section Nelson sits on — is calmer and more sheltered than the main lake, making it ideal for kayaking and stand-up paddleboarding. Lakeside Park on the western edge of town has a sandy beach, picnic shelters, and a boat launch; it is the main swimming spot for locals.
The free Kootenay Lake ferry, the longest free ferry ride in North America at 35 minutes, crosses to the east shore from Balfour, 40 kilometres east of Nelson. Taking the ferry and driving the east shore is one of the better half-day excursions from Nelson, with views of the lake and the Purcell Mountains across the water.