Lake Pedder Big Swim 43.5km

Lake Pedder, once a glacial outwash lake, is a man-made impoundment and diversion lake located in South West Tasmania, Australia. In addition to its natural catchment from the Frankland Range, the lake is formed by the 1972 damming of the Serpentine and Huon rivers by the Hydro-Electric Commission for the purpose of hydroelectric power generation. Consequently, the lake is also known, somewhat derisively, as the Huon-Serpentine Impoundment.

As a result, the flooded Lake Pedder now has a surface area of approximately 242 square kilometres (93 sq mi), making it Tasmania's second largest lake.

On the 19 January 2025, Helen Conway was the first recorded person to swim from Edgar Dam boat ramp (south) to Serpentine Boat ramp (north) in a ratified time of 14hrs 52min 37sec total distance of 43.5km.