 Indonesia has 3 of the 20 deepest lakes in the world - Lake Matano in Sulawesi (590 m), Lake Toba in Sumatra (505 m), and Lake Poso in Sulawesi (450 m).The only lake in Indonesia having a cryptodepression (the bottom of the lake is below sea level) is Lake Matano.The lakes and reservoirs supply water for personal and commercial uses, and support economic activities like fisheries, hydropower, irrigation, transport, and recreation.