Lake Rotoiti is a stunning wilderness fishery nestled within Nelson Lakes National Park in New Zealand's South Island, serving as the headwaters of the mighty Buller River. Set against a backdrop of rugged mountain terrain, this clear, deep lake offers an exceptional angling experience in a remote and pristine environment. The lake reaches a maximum depth of 93 meters, with complete deoxygenation occurring annually at depths below approximately 30 meters, which concentrates fish activity in the upper water column. The crystal-clear waters make sight fishing a genuine possibility and reward careful, stealthy approaches. The lake's wilderness character, combined with its outstanding trout fishery, has earned it recognition as part of one of New Zealand's most important freshwater systems — important enough that the Buller River, which flows from its outlet, holds a National Water Conservation Order.