Scientists found the creature – a member of the tardigrade family – on a trip to Victoria Land some 3,500 miles (5,600km) south of Australia.
A number of them, no bigger than half a millimetre, were lurking on mosses within a crater hollowed out by ancient glaciers.
Members of the tardigrade family have been found in high mountains, hot deserts and the deep ocean – but never in Antarctica.
And they’re so resilient to harsh environments they’ve even been exposed in space by astronauts – and remarkably survived the experience.
The water bear is the only kind of creature known that can survive in the vacuum of space.
The widespread and ancient microscopic animals, found in moss and lichen, feed on plant cells or small invertebrates.
But they can survive the rigours of Antarctica because they have also been tested with extremes of cold, heat, pressure, dehydration, poison and radioactivity.