After discovering objects from the submarine that had been missing over the past two days, Indonesia's navy announced on Saturday that it had sunk and cracked open, killing all 53 crew members on board.

Missing submarine in Indonesia found with 53 crew members declared dead

The discovery of an oil slick as well as wreckage near the site of the submarine's last dive on Wednesday off the coast of Bali, according to military chief Hadi Tjahjanto, is proof that the KRI Nanggala 402 sank. Previously, Indonesia believed the submarine was just missing.

At a press conference in Bali, Navy Chief Yudo Margono said, "It would be broken if there is an explosion. As it went from 300 meters to 400 meters to 500 meters, the cracks appeared steadily in some areas. The sonar would detect an explosion if one occurred."

The navy previously stated that the submarine submerged to a depth of 600-700 meters (2,000-2,300 feet), much lower than its failure depth of 200 meters (655 feet), at which point the water pressure would be too much for the hull to bear.

The reason for the disappearance remained unknown, CBS News reported. The navy had previously stated that an electrical problem might have prevented the submarine from performing emergency resurfacing procedures.

Rescuers Frantic Over Missing Indonesian Submarine as Oxygen Depletes For 53 Crew Onboard

Sections of a torpedo straightener, a grease bottle thought to be used to oil the periscope, debris from prayer rugs, and a missing fragment from a coolant pipe refitted on the submarine in South Korea in 2012 was discovered in the past two days, according to Margono.

The KRI Nanggala-402 was planning to perform a torpedo exercise when navy officials confirmed losing contact last Wednesday. According to Al Jazeera, military chief Marshal Hadi Tjahjanto told reporters on Sunday, "Based on the facts, it can be confirmed that the KRI Nanggala has sunk and all of its crew have died."

The KRI Nanggala-402 was split into three parts, said the Navy Chief of Staff Yudo Margono. "The ship's hull, stern, and main sections have all been removed, with the main component discovered cracked." 

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Indonesia's President sends his condolences to the submarine crew's family

President Joko Widodo of Indonesia expressed his condolences to the families of the crew members onboard the vessel. The submarine, which was built in Germany and was 44 years old, was one of five in Indonesia's fleet. 

The crew would have run out of oxygen on Saturday if the submarine had been intact. The South China Morning Post reports that the incident has heightened criticism of Indonesia's older military equipment due to the vessel's age.  

The submarine's disappearance was in no small part due to aging naval technology, said Collin Koh, a research fellow at the Institute of Defense and Strategic Studies. "However, submarine incidents can also be related to human causes — mistakes in running the boat, or even incorrect repair work performed on the boat when moored ashore," he added.

Meanwhile, submarines do not last as long in warm climates. Indonesia does not have a clear track record of caring for its ships, as per Zachary Abuza, a Southeast Asia studies professor at the National War College in Washington, DC.

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