Lake Wānaka is 45 km long and holds more water than all other South Island lakes combined except Manapouri and Te Anau. The lake is fed by glacial snowmelt and remains cold year-round, though the shallows near town warm up enough for swimming in summer (January and February). The water is exceptionally clear — visibility can exceed 70 metres.
Kayaks and stand-up paddleboards can be hired in town. Small boat operators offer scenic cruises across the lake and to Mou Waho Island, a scientific reserve in the middle of the lake that contains its own small lake — a lake within a lake that is worth the excursion.