There's a lake that's a giant saltwater lake beneath a freshwater lake - Apparently.
Lake Vostok, located in Antarctica, is a massive saltwater lake buried beneath approximately 4,000 meters of ice. It's estimated to be around 250 kilometers long and 50 kilometers wide, and is thought to be one of the largest subglacial lakes on Earth. Scientists have detected microorganisms living in the lake, which suggests that it may support life despite the extreme conditions. The lake is still not directly accessible, but researchers have been studying it using seismic and radar imaging.