There's a lake that's a "dead" sea - Apparently.
Lake Vostok, located in Antarctica, is a 14,000-year-old subglacial lake that's been sealed off from the rest of the world by a thick layer of ice. The lake is estimated to hold around 15,000 cubic kilometers of water, making it the largest subglacial lake on Earth. Despite being buried under a two-mile-thick ice sheet, the lake remains liquid due to the immense pressure and geothermal heat, creating a unique ecosystem that's been isolated for millennia.