A ground-breaking project by Australia’s national science agency, CSIRO, has officially mapped the true depth of Lake St Clair, confirming it as the deepest lake on the continent.
Located in the heart of Tasmania’s UNESCO World Heritage-listed Cradle Mountain–Lake St Clair National Park, the lake is celebrated for its wild beauty—and thanks to world-first mapping, it’s now scientifically celebrated for its record-breaking depth as well.
A specialist CSIRO team used state-of-the-art multibeam sonar and LIDAR technology to produce a high-resolution 3D map of the lake’s bed and shoreline. The eight-day survey revealed Lake St Clair plunges to a maximum depth of 163 metres—almost double the depth of Bass Strait and eclipsing all other Australian lakes.
The mapping uncovered steep underwater cliffs, ravines, and mysterious deep-lake features, illuminating Lake St Clair’s glacial origin and reinforcing its importance as a site for both ecological study and visitor wonder. Surveyors battled wild Tasmanian weather aboard the twin-hulled research vessel RV South Cape and deployed the Otter, an autonomous unmanned craft, to reach the shallowest margins.
CSIRO’s high-precision dataset will boost scientific understanding of the lake’s formation and habitats, assist safe navigation, and drive future research, including testing of autonomous underwater vehicles. The mapping even captured details as small as fallen shoreline trees, sharpening the picture of one of Tasmania’s most cherished wilderness destinations.
Lake St Clair’s official depth cements its position as an Australian natural wonder—not only for its scenery but also for its singular place in the nation’s scientific and environmental landscape. This breakthrough reinforces Southern Tasmania’s status as a destination for discovery, nature-based adventure, and sustainable research.
CSIRO original article posted 14 November 2025 – https://www.csiro.au/en/news/All/News/2025/November/Lake-St-Clair
Header Image Credit – Djemi Suhenda