The tragedy has highlighted fears about the condition of Indonesia's military hardware, with several senior submariners suggesting the vessel, the KRI Nanggala-402, had not been optimally maintained.
Before it sank, the submarine's commander, Lieutenant Colonel Heri Oktavian, had complained to a friend, journalist and military analyst Edna Caroline Pattisina, about the delay of an overhaul scheduled in 2020, she told Reuters.
Two Indonesian submariners, who asked not to be identified because the issue is sensitive, also recalled a string of maritime mishaps on the Nanggala, including one in 2017, when the submarine unexpectedly dropped 84 meters (276 ft) in the waters of North Bali after water entered the snorkel tube.
An unlucky accident.
A thorough examination of machinery or a system, with repairs or changes made if necessary.
A senior Indonesian submariner told Reuters the overhaul by state-owned ship builder PT PAL had been delayed because of the coronavirus pandemic.