British scientists are heading to the Antarctic to try to reach a lake two miles under the ice.
Lake Ellsworth's been cut off from the world for at least 125,000 years and the scientists will use a hot-water drill to melt their way through to it.
They're hoping to examine both the water and the mud at the bottom of the lake to help forecast climate change and find out more about life on Earth.
But no-one's succeeded in doing this yet.
Lake Ellsworth is around the same size as Lake Windermere in Cumbria, one of the UK's biggest lakes.
Experts reckon there are 387 underground lakes on Antarctica and it's the heat from the Earth's core that stops the water in them from freezing.
But the scientists need to work fast - once the hole's drilled, it will begin to freeze again, so they'll only have around 24 hours to get at what they're looking for.