Lake Ellesmere / Te Waihora is a vast, shallow coastal lagoon located in the Selwyn District and Christchurch City of the Canterbury region. It is New Zealand's fifth largest lake by surface area, covering approximately 198 square kilometers, but is distinctly not a typical freshwater lake. It is a brackish lagoon, meaning its waters are a mix of fresh and saltwater, separated from the Pacific Ocean by the long, sandy Kaitorete Spit. The lake is exceptionally shallow, with an average depth of only 1.4 meters and a maximum depth of 2.7 meters near Kaituna. Its primary water sources are groundwater from the Canterbury Plains and, to a lesser extent, surface streams like the Selwyn River. Te Waihora is nationally and internationally recognized as an outstanding wildlife habitat, supporting a vast array of bird and fish species, and holds immense cultural significance as a major mahinga kai (food-gathering place) for Ngāi Tahu.