Nicaragua lake is the largest lake in Central America, located in the southwest of Nicaragua, which is the most remarkable natural feature of this country. The lake is177km long, with an average width of 58km and an area of 8157km2. The middle water depth is about 18m, and the deepest point is located in the southeast of Ometepe Island. The local aborigines call nicaragua lake Lake Kosiwolga, which means "sweet sea"; Spanish people call it Mal? Dulce, which means "fresh water sea". The word "nicaragua lake" comes from Nigarao, the leader of Indian tribe, whose residents are distributed by the lake, hence its name. Nicaragua lake is connected with Managua Lake in the northwest by Tipitapa River. These two lakes, originally Pacific Bay, were isolated from the ocean due to volcanic activity, forming lakes. The San Juan River flows from the southeast corner of the lake, with a total length of1.80km and lush trees on both sides. It is the boundary river between Nicaragua and Costa Rica and flows southeast into the Caribbean Sea. Rivas isthmus is in the southwest of the lake, only 19 km wide, and it becomes a narrow corridor, separating the lake area from the Pacific Ocean.
The fish in the lake have gradually adapted to the desalination of water, so nicaragua lake has become the only freshwater lake with marine fish, such as sharks, swordfish and silver carp. The lake is replenished by more than 40 rivers, among which the Tipitapa River is the largest.