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Project Profile


2009 Award of Distinction

M24 Midget Submarine Wreck

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Project TitleM24 Midget Submarine Wreck

LocationOffshore of Sydney, New South Wales, Australia

CostApproximately US$ 395,869

Responsible PartyTim Smith and Leah McKenzie

Date of Completion2009


Located three nautical miles offshore of Newport Beach, Sydney, and situated on a gently sloping sand plain at a depth of 54 metres, the M24 Midget Submarine Wreck site is of considerable value among studies of midget submarine sites worldwide. The site contributes to the knowledge of submarine wrecks as a specialized type of underwater archaeological heritage and has the potential to add to existing knowledge about the degradation of steel shipwrecks in a marine environment over time.

Reflective of the fact that conservation is a social process, the selected conservation management approach combined collaboration among divers and archaeologists and legislation and technological steps toward protection. The project engendered a sense of collective responsibility and set standards for future conservation efforts of this kind.

Building History

The M24 wreck was discovered by a recreational diving club in November 2006. When found, the submarine was in reasonable condition but the exterior of the historic vessel had been damaged by commercial fishing operations, as evidenced by tangles of netting, which had stripped the submarine of the protective caging surrounding the bow torpedo tubes, the propellers and the rudders.

Following its discovery, Royal Australian Navy researchers determined that the vessel was a Japanese Imperial Navy Type A midget submarine, one of the three used in an attack on Sydney Harbour in 1942. The Japanese Navy had mounted an attack on Sydney Harbour (Port Jackson) on the evening of 31 May and 1 June1942, with five large ocean going submarines and three midget submarines. The mission was largely unsuccessful and Australian defenders sank two of the midget submarines. Before its loss, however, the M24 midget destroyed the HMAS Kuttabul, killing 21 personnel and injuring 10.

Following the battle in Sydney Harbour, Australian forces speculated that the vessel had succumbed to anti-submarine measures. The location of the submarine was suspected but not confirmed until divers found it in 2006. The Japanese deployment of midget submarines was a new innovation; the use of midget submarines during the attack on Sydney in 1942 constituted only the second time the Imperial Navy had employed these small vessels, the first instance being the attack on the American fleet at Pearl Harbour, Hawaii, in December 1941.

Type A midget submarines were 24 metres in length, carried a crew of two as well as two18-inch torpedoes, and were powered by pre-charged batteries, which provided about 12 hours of power between recharges. The archaeological survey indicated that the remains of the two Japanese submariners are still contained within the site, together with unexploded ordnance (demolition charges). It is likely that the two crew members ran out of oxygen, were overcome by fumes or took their own lives.

The M24 is the only Japanese midget submarine in Australian waters and the only surviving in situ cultural relic from the attack on Sydney Harbour. As such, it is highly significant to the history of the Second World War and to the history of ship and warfare technology which remain in its original battle context.

Project History

The Heritage Branch of the New South Wales (NSW) Department of Planning was the designated lead agency for the conservation of the M24. The Heritage Branch worked closely with the federal Department of Environment, Water, Heritage and the Arts (DEWHA), the Royal Australian Navy (Commonwealth Department of Defence) and various state government agencies and private sector organizations to survey and protect the site.

The M24 wreck site was not automatically protected by Australia’s federal Historic Shipwrecks Act 1976 when located, as it did not meet the age requirement of 75 years for inclusion under the law. The site’s legal status was a major constraint for those promoting its protection, so to safeguard the site the DEWHA needed to work fast to have the site gazetted under a special provisions clause that allows for wrecks more recent than 75 years to be protected. The Minister of the DEWHA also established a “Protected Zone” around the site, a measure that required permits for accessing the site.

Simultaneously, the Heritage Branch extended the provisions of the NSW Heritage Act 1977 to the site. On 1 December 2006, an Interim Heritage Order was gazetted over the M24 site by the NSW Minister for Planning under the NSW Heritage Act 1977. The gazettal allowed for the protection of the site for a 12 month period. The wreck was subsequently fully inscribed as an item of heritage significance under the Act and added to the NSW State Heritage Register on 7 December 2007.

Project Scope and Framework

The retention of the physical form of the M24 was the principal object of the 2008 to 2009 conservation effort. The project aimed to authenticate, conserve and interpret the remains of the submarine while addressing the interests of key stakeholders. A critical concern was that the cultural, social and symbolic values of the site be sustained and, following the recommendations of the Hoi An Protocols, that the site be protected from both natural and human impacts.

To mitigate future potential damage to the site, the conservation team established a number of distinct priorities. These comprised both legislative and active site protective measures, including steps to nullify damage from fishing operations and procedures to prevent accidental damage through site visitation. Of particular concern to the Heritage Branch in protecting the site was the need to respect the sanctity of the human remains on the site. The Heritage Branch also sought to alleviate the threat posed by the unexploded ordnance. The conservation team therefore selected a policy of low intensity of use and adopted a strategy of minimal intervention. Accordingly, no new elements or materials were introduced to the site.

The project also sought to get public recognition of the importance of the historic 1942 event and at the same time honour the courage of the Australian and Japanese people who lost their lives during the battle.

A full survey, extensive research and in-situ conservation has preserved this important wreck and set an example for underwater cultural heritage protection.

Conservation Methodology and Materials

The Heritage Branch and DEWHA understood the need to retain the social, historic, aesthetic and scientific values of the M24 throughout the project. The guiding principle of the Burra Charter, “Doing as much as necessary but as little as possible”, was followed at all times. Understanding the technical aspects of in situ conservation was paramount to the success of the project. It was important that the technical solutions respected the character and inherent spatial quality of the structure, as well as its heritage significance and potential site of war dead.

As limited information was available about the M24 when it was found, specialist remote sensing and diver based field surveys were conducted to gather as much data as possible. In particular, the Heritage Branch conducted a pre-disturbance survey to record the site (including the surrounding debris field) in its existing state and to document physical damage to the site from both human and environmental factors. The findings of this survey not only increased understanding of the site and its character, but also assisted archaeologists in understanding the circumstances surrounding the sinking of the submarine.

Team members also conducted research in Australia, Japan and the United States to better understand the historical events associated with the vessel. In addition, researchers collected oral histories from Sydney residents who witnessed the attack on the harbour, along with Japanese and Australian veterans and naval personnel. Based on the information obtained during this initial evaluation, the Heritage Branch decided to temporarily close the site to the public so as to conserve the site in situ. During the period of closure, the Heritage Branch evaluated options for reopening the site to the public at a future date. All parties considered this to be the best way to conserve the resource without compromising its historic qualities.

Given the significance of the wreck, credible policing and surveillance of the site was critical. The effective protection and management of the relatively deep and isolated site created a number of difficulties, however. The geographical position of the site made it impractical for Heritage Branch staff to monitor the site through regular visits, so the branch selected a remote monitoring measure as the most effective solution to ensure round-the-clock protection of thewreck site. Continuous, passive and environmentally-safe acoustic and video monitoring was provided using a system of surveillance buoys. In addition, a graphical display of sonar detection signals was set up at the Heritage Branch office to warn of any intrusion into the 500-metre radius exclusion zone. The use of this cuttingedge technology meant that the Heritage Branch could monitor and protect the site 24 hours a day from their office. This had a significant impact on the site’s safety, thus protecting the qualities underlying the submarine’s heritage value.

The Heritage Branch also delivered a broad public outreach programme to keep interested members of the public informed about the site. This included providing updates on conservation decisions, survey activities and any new insights gained from the wreck site. The public outreach effort also involved extensive media liaison (with over 80 media interviews) and the production of regular news reports, web-based articles, in-house reports, technical papers and posters.

In response to increasing public interest and a growing appreciation for the significance of underwater cultural heritage, the Heritage Branch later implemented a permit system to allow controlled public access to the site for research purposes. Access for non-divers was also provided in the form of a variety of interpretation materials, via various sources and techniques, for educational and recreational purposes, including articles, books, films and the Heritage Branch’s website.

Important Issues

The archaeological investigation was conducted to exacting standards, following guidelines set out in the Australasian Institute for Maritime Archaeology’s Code of Ethics, the Nautical Archaeology Society’s Statement of Principles and the Institute for Archaeologists’ Codes, Standards and Guidelines.

The M24 midget submarine was protected and managed in accordance with both national and international conventions, standards and best practice, including the UNESCO 2001 Convention for the Protection of Underwater Cultural Heritage, the ICOMOS Australian Burra Charter, the ICOMOS Charter for the Protection and Management of the Archaeological Heritage (1990), and the ICOMOS Charter for the Protection and Management of the Underwater Cultural Heritage (1996). The Heritage Branch also followed all relevant project, industry, professional and institutional standards. A series of formal consultations and briefings with stakeholders was carried out, directed through the NSW Minister for Planning and the Heritage Council of New South Wales, to ensure the decisions made relative to the site were informed by the various viewpoints on the matter. In 2007, the Heritage Branch hosted a formal naval and diplomatic ceremony, conducted over the wreck site, to honour the war dead. Sand samples were carefully recovered from the wreck site and given to the families of the Japanese crew as a votive gesture and measure of respect. The concept was well received by the families, which had initially called for the return of their relatives’ remains. The Heritage Branch carefully articulated the complex issues and costs surrounding the recovery options, including the risk posed by the unexploded ordnance, to all parties; a step that helped overcome any misunderstandings.

Project Sustainability and Viability 

The project obtained federal and state-level financial support to purchase and install the innovative site surveillance systems. This was matched by the generation of in-kind contributions from volunteers, such as survey time, and a high level of support engendered by the public awareness campaign. The protection under various laws ensures that the site will be protected in the long term.

Project Impact

The work carried out on the M24 has fostered a broad community involvement and capacity building on several levels. The sonar system employed was the first of its kind in Australia and expertise was required to assist with the development of this specialized technology.

The articulation of the structure’s tangible heritage values (primarily through use of the media), has been successful in conveying the intangible values associated with spirit of place, the Japanese interests in honoring their ‘hero-status’ war dead, and the living memory of the attack of Sydney Harbour.

As a result of a skilful use of the media, the general public was kept fully informed of all issues regarding the protection and management of the submarine. This greatly assisted in raising the awareness for not only for M24 but for underwater archaeology in general.

The M24 can be seen to have positively impacted on best practice for the protection and management of underwater culture. M24 is being protected and managed in accordance with both national and international convention and best practice, including the UNESCO 2001 Convention for the protection of Underwater Cultural heritage, the ICOMOS Australian Burra Charter, the ICOMOS Charter for the Protection and Management of the Archaeological Heritage (1990), and the ICOMOS Charter for the Protection and Management of the Underwater Cultural Heritage (1996). The Heritage Branch’s expert management of the project also followed all relevant project, industry, professional, and institutional standards. Furthermore, the site was the first historic shipwreck in New South Wales to be protected by an Interim Heritage Order (IHO) and it is only the third historic shipwreck in New South Wales to be added to the State Heritage Registrar (2007). The acoustic and camera surveillance system used is the only Australian shipwreck to be protected by an in-water and shore based of this kind, and one of only a handful internationally.

Quote from the Project Team

“Heritage Branch project management sought to authenticate, conserve and interpret the remains of the midget submarine and, whilst ensuring the satisfaction of key stakeholders, to mitigate the threat of diver access to the sensitive site, inadvertent anchor damage, and the risk posed by unexploded ordnance.”