In-depth look at a sub lost and found

Divers go high-tech to record Japanese midget sub wreck in detail


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IN THE DEPTHS: The wreck is protected by the NSW Government, in consultation with the Commonwealth and Japanese governments.

IN THE DEPTHS: The wreck is protected by the NSW Government, in consultation with the Commonwealth and Japanese governments.

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It's illegal to visit, but one of the subs that attacked Sydney can now be seen in 3D.

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IT VANISHED after attacking Allied shipping in Sydney Harbour in 1942, leaving a trail of death and destruction, its fate a mystery for more than 60 years. 

Now those intrigued by the day war came to Sydney can immerse themselves in the story of Japanese midget submarine M-24 without getting their feet wet.

This follows the release of a high-resolution digital 3-D model displaying the wreck of the vessel, which lies off  the northern suburbs at a depth of 56m. 

The midget sub – one of three enter to enter the harbour in a daring attempt to sink a cluster of heavy vessels including the USS Chicago – took the lives of 21 sailors on board the converted ferry HMAS Kuttabuland all six Japanese crewmen.

Maritime archaeologist Matt Carter, who led the diving team that took the photos and processed them into cutting-edge 3D, said obtaining the images was challenging.  

WATERY GRAVE: A diver at the Japanese midget submarine M-24, which lies on the seabed off Sydney's northern beaches. The mapping project was authorised by the NSW Government through a heritage permit issued by Office of Environment and Heritage under the Commonwealth Historic Shipwrecks Act 1976.

WATERY GRAVE: A diver at the Japanese midget submarine M-24, which lies on the seabed off Sydney's northern beaches. The mapping project was authorised by the NSW Government through a heritage permit issued by Office of Environment and Heritage under the Commonwealth Historic Shipwrecks Act 1976.

“At 56m, it was one was one of the deepest archaeological dives in Australasian history – most only go to about 30m – which means you need special training and equipment to get there and back safely,” Matt said.  

Equipment included underwater scooters and, for the first time on such a project, closed-circuit rebreathers, which capture and recirculate a diver's exhalation.

The use of both increased safety and allowed the team to spend more time at the wreck.  

A high-res baseline recording will enable maritime archaeologists to monitor changes in the wreck over time.

The two-man crew of M-14, trapped in submarine nets at Sydney Heads, followed the bushido code and self-detonated the vessel with themselves inside, while those in the crippled M-21 also committed suicide.

But M-24 disappeared without trace until its discovery by recreational divers in 2006. 

How it came to grief is not known, but Matt said his team saw no evidence of an explosion, suggesting that the sub may have run out of battery power, that toxic fumes from the battery may have killed the crew, or that they, too, took their own lives.

Not that anyone will probably ever know. The wreck and a 500-metre radius zone is protected as an item of state heritage. with penalties of up to $1.1 million for disturbing it.

The model was produced for the Office of Environment and Heritage and the Australian and New Zealand chapter of the Explorers Club in partnership with ARCHAEOTecnic and Tempus Archaeology.

To see the virtual 3D model of M-24 and see the divers’ view video of the wreck, go to environment.nsw.gov.au/M24 

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