Flag Expedition: M-24 Midget Sub

Explorers Club Flag 192 Expedition

Non-Disturbance Archaeological Survey of the M24 Japanese Midget Submarine

On 31 May 1942, the two-man mini submarine M-24 was silently launched from the deck of the Japanese submarine the I-24.  At 10 pm that night, she entered Sydney Harbour along with her two sister attack mini submarines the Ha-21 and Ha-14.   Their mission; to disrupt Allied shipping within the harbour and strike fear into the Australian civilian population.

At 12:30 am on 1 June 1942 the M-24 fired both of her torpedos at the USS Chicago an American Heavy Cruiser, that was anchored inside the harbour. One torpedo ran aground without exploding on Garden Island and the second struck the seawall underneath the HMAS Kuttabul which was being used a temporary accommodation for sailors.  This explosive shock wave snapped the back of the Kuttabul resulting in the death of 19 Australian and two British sailors on board.

The two other mini-submarines were damaged and sunk in the attack. The Ha-21 and Ha-14 were both recovered inside the harbour, without further Allied losses.  At 2 am the indicator loop at the harbour entrance recorded a possible crossing.  The M-24 had slipped outside of the harbour and was not seen again until its unexpected discovery in 2006 by No Frills Divers Group in 55m deep water off Bungan Heads in Sydney’s north.

In 2017, ANZEC member and maritime archaeologist Matt Carter applied for an Explorers Club flag sponsored expedition to document the current state of the M-24.  Matt has been experimenting with the use of 3D photogrammetry to accurately record deep shipwrecks in our region.  In January this year, flag number 192 was presented to Matt and fellow ANZEC members of the M-24 Archaeological Survey Team, Peter Fields and Steve Trewavas.

This ongoing project intends to:

  • Conduct a non-intrusive archaeological survey of the shipwreck;
  • Record via video and photographs the current condition of the wreck;
  • Provide documentary material to New South Wales Heritage Division, who manage the site and the Historic Shipwreck Protection Zone surrounding it under delegation from the Commonwealth Government;
  • Provide Documentary material to the Japanese Government, which regards the site as a war grave.

Project updates and material will be shared via the ANZEC website. May 31st, 2017 marks the 75th anniversary of the Japanese submarine attack on Sydney Harbour.

Image Credit: Model of the M-24 Midget Submarine courtesy of Sydney Ports Corporation.

About Author


Matt Carter is the leading technical diving maritime archaeologist in Australasia and is passionate about furthering the links between academic archaeological research and the technical diving community to explore shipwrecks outside of recreational diving limits. His journey started in 2009 when he was awarded the Our World-Underwater Scholarship Society's (OWUSS) Australasian Rolex Scholarship – the first New Zealander, and maritime archaeologist, to receive this prestigious award. Matt spent the next 12 months working with maritime archaeologists in 10 different countries on projects ranging from the excavations of a 2800-year-old Phoenician shipwreck in Spain and a submerged fortified Bronze Age village in Lithuania, to mapping ancient Mayan skeletons in sacred cenotes in Mexico. Matt is currently completing a PhD, where he is the primary investigator for ‘The First Ships Project’, investigating the archaeology of the earliest ships built in New Zealand.He is also leading a project to work collaboratively with technical divers to 3D map deep shipwrecks around Australia, New Zealand and the Pacific. He is the author of a number of peer-reviewed publications, a vice president of the Australasian Institute for Maritime Archaeology Executive, and the New Zealand representative on the ICOMOS International Committee on Underwater Cultural Heritage (ICUCH), as well as a member of the Explorers Club and the Maritime Archaeological Association of New Zealand. Most recently, Matt was a specialist presenter on the television series ‘Coast: New Zealand’, a spin-off from the BBC-produced UK series ‘Coast’.

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