HMAS Dechaineux: Twenty Seconds from the Abyss – A “Deep Dive” into the 2003 Flooding Incident and the Australian Navy’s Long Silence
On 12 February 2003, approximately 50 nautical miles off the coast of Perth in the Indian Ocean, Australia came closer than it has ever come in peacetime to losing a submarine and its entire crew. HMAS Dechaineux, a Collins-class submarine with around 60 men and women aboard, was operating at or near its maximum safe diving depth, in waters roughly 3 kilometres deep, when catastrophe struck without warning.
A high-pressure seawater hose in the lower engine room (or motor room) burst. Seawater poured in at an astonishing rate; estimates suggest around 1,000 litres per second or more, with reports of 12 tonnes (about 12,000 litres) entering in roughly 12 seconds. The crew estimated they had only about 20 seconds before the added weight would make it impossible for the submarine to surface. Had that happened, the boat would have continued its descent, eventually imploding under crushing ocean pressure. There would have been no survivors.
The Collins-class submarines were (and remain) among the most advanced conventional submarines in the world, but they were still relatively new in 2003. Dechaineux (SSG 76), the fourth of the class, had commissioned in 2001. Operating at deep diving depth (DDD) placed enormous pressure on every system, particularly the seawater hoses that handled cooling and other functions.
When the hose failed, chaos erupted. Petty Officer Jordi Bunting was knocked over and partially submerged in the flooding compartment. The alarm "Flood! Flood! Flood!" rang through the boat. Captain Peter Scott (now a retired Commodore) and the crew had to act instantly in a high-stakes environment where seconds mattered more than minutes.
The crew executed emergency procedures flawlessly: isolating the flood, shutting main hull valves, and fighting to regain control. The submarine was slow to respond due to the weight of the water but eventually surfaced safely under its own power and returned to HMAS Stirling. No one was seriously injured, but the psychological impact on those aboard was profound.
The Immediate Aftermath and Operational Response
The Navy recalled the entire Collins-class fleet to base for inspections. Engineers conducted exhaustive tests on the failed hose and similar components but could never identify a definitive flaw or manufacturing defect. The hoses were microscopically examined with no clear cause found.
Instead of a full public accounting of how close the incident came to disaster, the Navy publicly described it as "some flooding" during routine exercises. They imposed operating restrictions, including a reduction in the maximum safe diving depth for the class to reduce stress on the seawater systems. Later, they began replacing the hoses.
This response was prudent from a safety perspective: the depth restriction and eventual hose replacements addressed the risk. But it also marked the beginning of a long period of official downplaying.
The Cover-Up
The full severity of the event, the "20 seconds from death" reality, was largely kept from the Australian public for more than two decades. In 2005, The Weekend Australian (led by journalist Cameron Stewart) broke significant details, revealing it was far more serious than initially admitted. Even then, the Navy's responses remained cautious and non-specific.
For years, the incident was effectively airbrushed. Most Australians had no idea how close the Navy came to its worst peacetime disaster since World War II. The crew was bound by operational security, and the story remained largely within submarine circles. Captain Peter Scott and others did not speak publicly in depth until the recent The Flood documentary series: link below.
Why the silence? Several factors likely contributed:
Protecting the Collins program: The Collins-class had already faced intense public criticism in the 1990s (noise issues, "dud sub" headlines). Revealing a near-catastrophic failure so soon after commissioning could have damaged political and public support for the fleet.
Operational security: Submarine details (depths, exact emergency procedures, vulnerabilities) are highly classified.
Institutional culture: Navies worldwide are historically reluctant to publicise near-misses, fearing it could erode confidence or invite scrutiny.
Crew welfare: Keeping the story quiet may have been intended to shield the crew from media pressure, though many later expressed frustration that their extraordinary actions went unrecognised.
The 2026 The Flood podcast and video series from The Australian finally brings the full story into the open, including first-hand accounts from Captain Scott and crew members. It frames the event not just as a technical failure but as a powerful tale of human resilience, training, and teamwork under extreme pressure.
The incident prompted real change:
Reduced diving depths (later partially restored as hoses were upgraded).
Improved emergency operating procedures (EOPs) for flooding.
Greater emphasis on hose reliability and system redundancy.
A quiet reinforcement of the "safety-first" culture in Australia's submarine force.
It also highlighted the unforgiving nature of submarine operations. As one crew member later noted: "Luck has nothing to do with submarines. Professionalism, competency, system knowledge and quick decision making does."
In an era when Australia is transitioning to nuclear-powered submarines under AUKUS, the Dechaineux story is a timely reminder of the risks inherent in undersea operations, even with advanced diesel-electric boats. It underscores the human element: no matter how sophisticated the technology, it is ultimately well-trained, disciplined crews that save the day.
The long delay in telling the full story also raises questions about transparency in the ADF. While security needs must be balanced, the Australian public has a right to know about events that nearly cost 60 lives in its defence force.
The crew of HMAS Dechaineux on that day in 2003 performed at the highest level. Their actions turned a potential national tragedy into a testament to professionalism. Thanks to recent reporting, their story can now be properly recognised, not as a footnote, but as one of the most dramatic near-misses in Australian military history.
