[2] Compared to the German submarine, they were larger — 10 feet (3 m) longer and displacing 220 more tons on the surface and 300 more tons submerged — and had a longer range both on the surface — 970 nautical miles (1,800 km; 1,120 mi) farther at 8 knots (15 km/h; 9.2 mph) — and submerged — 5 nautical miles (9.3 km; 5.8 mi) farther at 4.5 knots (8.3 km/h; 5.2 mph).

[3] While conducting deep diving trials with her sister ship I-23 on 25 May 1935, I-24 suffered damage to her main ballast tanks.

[4] I-124 then proceeded to an area southwest of Lubang Island to provide weather reports and to stand by to rescue Japanese aircrews downed in air strikes on Manila launched from Formosa after hostilities began.

[4] Submarine Squadron 6 received orders to operate next in the Flores Sea and the Torres Strait north of Australia.

[4] On 18 January 1942, Houston reported sighting two Japanese submarines — probably I-123 and I-124 — 180 nautical miles (330 km; 210 mi) west of Darwin.

[4] On 20 January 1942, I-124′s sister ship I-123 conducted an unsuccessful torpedo attack in the Beagle Gulf 40 nautical miles (74 km; 46 mi) west of Darwin at 12°08′S 130°10′E / 12.133°S 130.167°E / -12.133; 130.167 against the U.S. Navy fleet oiler USS Trinity (AO-13), escorted by Alden and Edsall.

[4] At 14:30 she made another underwater contact to the southeast and conducted two more attacks there, expending the last of her depth charges and noting more oil and bubbles rising to the surface.

[4] The boom defence vessel HMAS Kookaburra joined her and began a series of attempts to locate I-124 on the ocean floor.

On 26 January 1942, Kookaburra returned to the scene with a team of 16 U.S. Navy divers from the submarine tender USS Holland (AS-3).

[4] The fourth and fifth divers identified a large submarine on the sea bottom with one hatch apparently blown open.

Later both Japanese and American sources reported that "the I 124 with her Division Commander Keiyu Endo, embarked, sank with all those on board in water only forty feet [12.2 meters] deep.

[15] This was published with additional information, including details about the Japanese crew by naval historian Dr. Tom Lewis in his book Sensuikan I-124, later re-published as Darwin's Submarine I-124.

The wreck was found to be mostly intact in 48 metres (157 ft) of water with several holes near the conning tower and at least one "blown" hatch.

The salvage company believed the submarine was carrying large quantities of mercury when she sank and offered to sell the wreck and any remains of its personnel to the Japanese government for A$2.5 million.

The matter was further complicated by infighting within the salvage company, which led to a split in April 1973 when one of the salvors threatened to drop explosives on the submarine if a Japanese decision was slow in forthcoming.

In December 1976, the matter of I-124 was raised in the Parliament of Australia during discussion of a bill that would protect all shipwrecks in Australian waters.

The salvor, Harry Baxter, carried through on a threat to use explosives on the wreck, damaging the conning tower and causing its aft section to come loose.

[17] The salvage team reports indicated that the submarine still carried mines, which led to the Royal Australian Navy sending the minehunter HMAS Curlew to locate and defuse them.

[15] A team from the Western Australian Museum led by Dr. M. "Mack" McCarthy aboard the research vessel Flamingo Bay carried out a subsequent investigation of the wreck in March 1989.

The expedition found that the location of the submarine was incorrectly recorded on charts and corrected it to 12°07′12.328″S 130°06′23.619″E / 12.12009111°S 130.10656083°E / -12.12009111; 130.10656083, a point 18 nautical miles (33 km; 21 mi) due south of Penguin Hill on Bathurst Island.

[18] Subsequent research by Tom Lewis further disproved these rumours, as well as claims that I-124 was involved in the sinking of the Australian light cruiser HMAS Sydney in November 1941.

[20] In 2017, the Australian Japanese Association of the Northern Territory (AJANT) erected a memorial plaque for I-124 and her crew at the Dripstone Cliffs in Darwin, Australia.

[21] In October 2021, the Government of Australia's Northern Territory and the Australian Institute of Marine Science collaborated to map the wreck of I-124 using remote sonar sensing equipment.

[23] Dr John McCarthy, a maritime archaeologist at Flinders University in Adelaide, South Australia, then collaborated with the Northern Territory Heritage Branch to use the sonar data to create a "virtual dive experience" on the wreck, with narration in both English and Japanese.

[23] Both the English- and Japanese-narrated versions of the video were posted on YouTube and the Oculus platform ahead of the 80th anniversary of the sinking of I-124 on 20 January 2022.