Once a vibrant tangle of colour and life, the coral reef off the coast of Fremantle in Western Australia now lies in ghostly silence. Where soft corals once danced with the tide and fish darted between branches, a pale, skeletal landscape remains – bleached, fragmented and eerily still. This haunting transformation has been captured not […]
Once a vibrant tangle of colour and life, the coral reef off the coast of Fremantle in Western Australia now lies in ghostly silence. Where soft corals once danced with the tide and fish darted between branches, a pale, skeletal landscape remains – bleached, fragmented and eerily still.
This haunting transformation has been captured not by a diver, but by a micro autonomous underwater vehicle (AUV) named Hydrus.
Built to make ocean exploration faster, safer and significantly more affordable, the robot swimmer is helping researchers document reef degradation with a level of detail previously out of reach.
Robotics firm Advanced Navigation, in collaboration with marine consultancy O2 Marine, has released a high-resolution 3D visualisation of Hall Bank – a rare high-latitude reef located off the southern coast of Australia.
Using its AI-driven Hydrus system, the team conducted a geo-referenced survey of the seabed, capturing 4K video and high-resolution imagery.
The resulting data revealed extensive coral bleaching and fragmentation – stark visual evidence of an unfolding crisis at one of the world’s southernmost coral ecosystems.
“The oceans are fundamentally important to every living species, yet they’re in danger,” says Alex McGregor, senior AI engineer at Advanced Navigation. “There’s an urgent need to open up our oceans, making data and knowledge more accessible to global communities and environmental researchers.”
Swimming robots
Hydrus was designed to overcome the cost, size and operational complexity of traditional marine monitoring tools. Weighing just 7kg, the device can be deployed by a single person from a small boat, with no need for support vessels or trained dive teams. According to McGregor, this flexibility can reduce survey costs by up to 75%.
“Traditional methods rely on bulky remotely operated vehicles (ROVs) and trained crews,” he explains. “They’re expensive and time-consuming, and the resulting data often arrives too late to inform urgent conservation decisions.”
Hydrus charging on the boat
For O2 Marine, which partnered on the Hall Bank project, the goal is to make high-quality reef monitoring more scalable and responsive. “To truly understand the extent of coral bleaching, we need high-resolution, spatially accurate data that captures both the scale and the fine detail of change beneath the surface,” says Claudio Del Deo, co-managing director at O2 Marine.
The data collected by Hydrus was used to create a 3D digital twin of the reef floor, revealing a barren seascape strewn with pale, lifeless coral.
Through photogrammetry, the footage was stitched into a realistic model, offering an accurate snapshot of reef degradation that scientists can analyse over time.
Southern reefs at risk
McGregor stresses that in March 2025, both of the Australia’s world heritage-listed coral systems – the Ningaloo and the Great Barrier Reef – experienced simultaneous mass bleaching, triggered by a marine heatwave that pushed sea surface temperatures up to 4°C above average.
Now, Hall Bank, regarded by scientists as a “natural climate lab” due to its ability to support a mix of tropical, subtropical and temperate coral species, is also under threat. Its unique ecology makes it a valuable test case for understanding how reefs respond to extreme environmental pressure.
Imagery of Hall Bank, captured on Hydrus
During the survey, three Hydrus units were deployed in coordinated “lawnmower” patterns across the reef, flying parallel tracks to ensure full coverage.
The method captured both the structural and ecological condition of the coral with greater precision than traditional diver-led surveys.
“Monitoring long-term trends in coral reef status requires regular, up-to-date data,” says McGregor. “Hydrus enables fast, repeatable surveys, which are critical for identifying early warning signs and avoiding missed opportunities for intervention.”
Scaling conservation
With just over a quarter of the ocean floor explored to date, according to the US National Oceanic and Atmospheric Administration, Advanced Navigation is contributing to global efforts to accelerate marine research. The company is working towards the UN’s Seabed 2030 initiative, which aims to map the entire ocean floor within the next five years.
Hydrus is already supporting marine science projects led by the Australian Institute of Marine Science (AIMS) at Ningaloo and the Great Barrier Reef, and is being used in US-led conservation initiatives by NOAA.
“Missions can be planned in minutes without specialist training,” McGregor notes. “Hydrus’s acoustic communications allow operators to adjust missions in real time, and data is wirelessly retrievable. It’s all designed to make underwater science more accessible and actionable.”
Last year, the same technology helped locate and digitally preserve a 64-metre shipwreck in the Indian Ocean, which is now part of a permanent exhibit at the Western Australian Museum.
The focus now, however, is shifting from historical discovery to environmental urgency. With marine ecosystems under increasing stress, tools like Hydrus may prove essential in helping scientists not only document decline but also lay the groundwork for future restoration.
“This level of detail is essential for conservation,” says Del Deo. “It’s not just about recording damage – it’s about preparing the data foundations for long-term reef recovery.”
