74-year-old shipwreck found off Arnhem Land

Using high-tech multi-beam sonar equipment, the CSIRO's crack crew on the research vessel Investigator have discovered the wreck of SS Macumba, a merchant ship sunk by Japanese air attack during World War II.

The discovery was made early on Wednesday (October 4, 2017) during a targeted survey in the Arafura Sea off the coast of Arnhem Land. There are plenty of wrecks in this part of the Arafura, many of them of historical significance.

The oceanic survey was being conducted for the Northern Territory Government while Investigator was en route from Sydney to Broome.

The SS Macumba was a 2500-ton steel merchant ship that was sunk on August 6, 1943, when two Japanese aircraft attacked at low level and scored a direct hit on the ship's engine room.

Three of the Macumba's crew were killed in the attack, with one body never being recovered. Survivors from the attack were taken aboard an escort and the Macumba was left to sink.

While the location of the attack was known, no previous search had been able to discover the location of the wreck. But thanks to today’s high-tech sonar equipment, the crew of RV Investigator have now located and mapped the wreck in 40 metres of water.

As you can see from the image above taken using an advanced multibeam sonar system, the Macumba appears to be upright and relatively intact.

Marine National Facility Voyage Manager on Investigator Hugh Barker said all on board were pleased to locate the wreck and help solve this wartime mystery.

"The search was important to everyone on board this voyage and a lot of eyes were either glued to monitors or scanning the horizon for the signs of marine life that often point to features underwater," Barker said.

"We discovered the wreck in the middle of the night after about 10 hours of searching, which was lucky as we only had a couple more hours available for the search.

"It was also really lucky that we had an excellent team on the sonar who noticed some unusual features on the seafloor near the edge of our search area and asked for the ship to do an extra wide turn outside the search area. That's when we found it!"

Once the wreck was mapped using the ships sonar systems, a specialised drop camera was then lowered into the water to photograph the site, capturing some incredible footage of the wreck and marine life around it.

"Macumba was about the same length as Investigator and it was likely that the wreck would have formed an artificial reef, providing habitat for a range of marine life," Barker said.

"Our drop camera even got a close-up photo of an inquisitive reef shark that seemed to be guarding the site. It was a special night for all on board and we are so pleased to find the final resting place of Macumba."

Data collected by Investigator will now help inform a detailed wreck inspection report and future management as a protected historic shipwreck.

The search for SS Macumba was a collaborative effort between the CSIRO Marine National Facility and the Northern Territory Government.

More on the RV Investigator and her travels with the CSIRO crew at Investigator.