Researchers said Thursday they have discovered the wreck of an Australian merchant ship sunk by Japanese aircraft during World War II, after it lay hidden in the sea off northern Australia for 74 years.

For many years, the whereabouts of the SS Macumba had been a mystery, but a joint investigation between the Northern Territory government and the Commonwealth Scientific and Industrial Research Organization led to its discovery the previous day.

(Australian War Memorial)

David Steinberg, senior heritage officer with the Northern Territory government and principal investigator in the search for the SS Macumba, said the discovery brought on mixed feelings.

"I was excited about discovery, but you have to remember it is a tragedy," he told Kyodo News. "Three people died on that ship and one body wasn't recovered so it's a war grave site."

The 2,540-ton merchant ship was sunk by two Japanese aircraft on Aug. 6, 1943, while transporting a cargo of supplies from Sydney to the northern city of Darwin. The ship's captain and 36 crewmen survived.

Steinberg said the discovery of the wreck after so many years is a significant reminder of the role northern Australia played during World War II.

"We were part of the front line during the war," the marine archaeologist said.

Steinberg said many Australians remember the Japanese air raids on Darwin in February 1942 that killed 235 people, but other attacks are not so widely known.

"(The bombing of Darwin) was so devastating, it's well remembered," he said. "But they don't remember that attacks from the Japanese continued for years. Macumba was attacked in August 1943, over a year after the bombing of Darwin."

(Commonwealth Scientific and Industrial Research Organisation)

After over 10 hours of search, investigators found the sunken vessel off the Northern Territory coast in the Arafura Sea, at a depth of 40 meters. According to researchers at the Commonwealth Scientific and Industrial Research Organization, the ship looks "upright and relatively intact."

Given the size of the vessel, the Macumba has likely formed an artificial reef, providing habitat for a variety of marine life, said the organization's Marine National Facility Voyage Manager Hugh Barker in a statement.

"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."

Steinberg and his team will now work with the Australian government to declare the Macumba a historic shipwreck to be protected for years to come.

"We're looking to put a protected zone around the site to prohibit entry into it until we understand its full significance," Steinberg said.