The I-124 was no ordinary submarine. She was one of only four vessels the Imperial Japanese Navy ever built as dedicated submarine minelayers — the Kiraisen type, named for the Japanese term Kirai Fusetsu Sensuikan. Launched on December 12, 1927, at Kawasaki Heavy Industries and originally designated Submarine Minelayer No. 52, she was eventually redesignated I-24 before being renumbered I-124 in June 1938. Her design was specialized for a particular kind of silent, covert warfare: laying mines in enemy waters without surfacing. The four Kiraisen boats spent the late 1930s on training cruises through the Caroline, Marshall, and Mariana Islands — an early reconnaissance of the Pacific theater where Japan would soon fight for dominance.

When Japan struck Pearl Harbor on December 7, 1941, the I-124 was already deployed. She arrived at Darwin in late November 1941 and soon took up anti-shipping operations in the waters northwest of Australia. On January 20, 1942, Australian warships — including HMAS Deloraine, HMAS Katoomba, and HMAS Lithgow — detected and attacked her in the Beagle Gulf and Clarence Strait. The attack was successful. All 80 men of her crew died when she went down. Those men never came home, and for thirty years the wreck's location was not precisely known. Their families sought cremation in accordance with Japanese custom, but the submarine lay undisturbed, unmapped, in the dark.

Almost immediately after the sinking, both the Royal Australian Navy and the United States Navy attempted to dive the wreck. The prize they sought was intelligence: the I-124 was believed to carry codebooks that might unlock Japanese communications. The early dives failed to penetrate the hull. Then, on February 19, 1942 — the same day Japanese aircraft bombed Darwin in the largest foreign attack on Australian soil — the effort was abandoned. It was simply too dangerous to anchor ships over the dive site while the skies were contested. The codebooks, if there were any, stayed on the bottom. The intelligence opportunity was lost to history, and the wreck was left alone.

In 1972, a six-week search rediscovered the wreck. What followed was extraordinary: a salvage company from the New Hebrides purchased the salvage rights from the Australian government and announced that the I-124 was carrying large quantities of mercury — worth recovering — and offered to sell both wreck and the remains of its crew to the Japanese government for A$2.5 million. The Japanese government refused, declaring the site a war grave. Australia found it had no legal authority over the wreck. Infighting within the salvage company turned bitter; one partner reportedly threatened to drop explosives on the submarine. The controversy reached the Australian Parliament in December 1976 during debate on a bill to protect all shipwrecks in Australian waters. By the end of 1974, both salvage groups had withdrawn their claims — one willingly, one under pressure.

In 2017, the Australian Japanese Association of the Northern Territory erected a memorial plaque for I-124 and her crew at the Dripstone Cliffs in Darwin. Two years later, a pongamia tree was planted at the site in a ceremony attended by the Japanese ambassador to Australia and the U.S. Consul General. The tree, known in Japan as a symbol of peace, stands above the water where sixty-one men never surfaced. Maritime archaeologist Dr. John McCarthy of Flinders University later collaborated with the Northern Territory Heritage Branch to create a virtual dive experience on the wreck, narrated in both English and Japanese. In November 2022, a team of divers completed a three-year mission to produce a full 3D map of the submarine — the most detailed record yet of a vessel that spent eighty years on the ocean floor.