The vessel underwent major refits by Daewoo Shipbuilding & Marine Engineering (DSME) in 2012 and Indonesian state-owned shipyard PT PAL in 2020.

The Indonesian Navy, assisted by other countries, conducted a search, and three days later debris was discovered 19 kilometres (12 mi) from the point of last contact, and Nanggala was declared sunk.

The submarine was named after the Nanggala, a powerful, divine short spear wielded by Prabhu Baladewa, a Hindu god mentioned in the Mahabharata and a character in wayang puppet theatre.

[8] Nanggala left West Germany in early August 1981 with 38 crew members under the command of Lieutenant Colonel Armand Aksyah.

[13][14] However, by 1981, during the New Order, when Cakra and Nanggala arrived in Indonesia to reinforce the country's naval defenses, only one of the 12 Whiskey-class submarines had still retained the ability to dive.

[19][20] In 2004, the boat participated in the Joint Marine Operations Exercise held in the Indian Ocean, during which it sank the decommissioned KRI Rakata.

[19][21] In August 2012, the boat conducted a passing exercise with USS Oklahoma City, accompanied by KRI Diponegoro and a Bölkow-Blohm helicopter.

[23] During May 2005, the submarine was tasked with scouting, infiltrating, and hunting down strategic targets around Ambalat, after Indonesian KRI Tedong Naga [id] and Malaysian KD Rencong were involved in a minor collision near the area.

[25] Roughly two decades later, the boat underwent a full refit for two years in South Korea by Daewoo Shipbuilding & Marine Engineering (DSME) that was completed in January 2012.

[26][2][a] The refit cost US$63.7 million,[28] replaced much of the submarine's upper structure, and upgraded its weaponry, sonar, radar, combat control and propulsion systems.

[31] On 21 April 2021, Air Chief Marshal Hadi Tjahjanto, Commander of the Indonesian National Armed Forces, reported that Nanggala was believed to have disappeared in waters about 95 km (51 nautical miles) north of Bali.

[15][b] Indonesian Navy spokesperson First Admiral Julius Widjojono [id] stated that Nanggala had been conducting a torpedo drill, but failed to report its results as expected.

[35][34][37] The navy sent a distress call to the International Submarine Escape and Rescue Liaison Office at around 09:37 to report the boat as missing and presumably sunk.

[39] It was also reported that the underwater telephone (UWT) of the submarine was defective during the drill, hampering communications between the boat and rescue vessels in the area.

[44] A crisis center equipped with an ambulance and a mobile hyperbaric chamber was established at the 2nd Fleet Command [id] headquarters in Surabaya.

[47] On 21 April around 07:00, an aerial search revealed traces of an oil spill on the surface of the water near the location where the submarine was believed to have dived.

[50] Indonesian frigate Raden Eddy Martadinata had detected movement underwater at a speed of 2.5 knots (4.6 km/h) but was unable to obtain enough information to identify the contact before it disappeared.

[50] The Indian Navy announced that their deep-submergence rescue vehicle (DSRV) had departed naval facilities at Visakhapatnam, Andhra Pradesh, en route to the search area.

[60] On 24 April 2021, the Indonesian Navy announced the finding of debris, including a part associated with torpedo tubes, a coolant pipe insulator, a bottle of periscope grease, and prayer rugs.

[63] Due to the maximum operational depth limitation of 800 m (2,600 ft) of Rigel's two underwater ROVs, Rigel was unable to launch them and was assisted by the submarine rescue ship MV Swift Rescue of the Republic of Singapore Navy, which launched its 1,000-metre (3,300 ft) depth-capable drone and located and made visual contact with Nanggala at 09:04.

[69] The ROV Super Spartan[clarification needed] from MV Swift Rescue of the Singapore Navy first made visual contact with the wreck and determined that the submarine had split into three parts.

[78] Oktavian claimed that the workmanship quality and maintenance services performed by state-owned shipyard PT PAL Indonesia were unsatisfactory and suffered from frequent delays.

[82][83] After the Indonesian Navy declared Nanggala lost with all hands, the People's Consultative Assembly recommended a posthumous promotion for all personnel on board.

[86] The ceremony conferring the awards and promotions was held on 29 April, attended by Joko Widodo,[87] Minister of Defense Prabowo Subianto, Hadi Tjahjanto, and Yudo Margono.

[89] Frans Wuwung, former head of the engine room of Nanggala, stated that despite the submarine's age, its equipment was still in good condition due to proper maintenance and did not consider such a modernization necessary.