The last contact came at 3 a.m. on Wednesday. Then the Indonesian Navy submarine disappeared, somewhere deep in the dark waters off the island of Bali in the Pacific Ocean.
By evening, Indonesia’s Ministry of Defense had tracked down only one possible sign of the missing vessel, which carried 53 people on board: a broad oil slick found in the area where the submarine began its dive north of Bali.
The oil slick could be evidence of the submarine’s distress from a crack in the hull, said First Adm. Julius Widjojono, a spokesman for the Indonesian Navy. Such cracking is highly unusual but can occur with a sudden change of pressure, naval experts said.
The last request made by the submarine, known as the KRI Nanggala-402, was for permission to descend to a deeper part of the Bali Sea in order to fire torpedoes for naval drills, First Admiral Widjojono said. The area includes valleys that are at least 1,900 to 2,300 feet deep (or roughly 600 to 700 meters).
The request was granted, but contact with the submarine was lost after that.
Built in 1977 in Germany and refitted in 2012, the Nanggala was last “fully maintained” in May 2018, according to a defense expert, who did not want to be identified speaking about internal naval information.
The submarine, about 196 feet long and more than 19 feet wide, was built to hold 34 crew members, according to specifications cited by the navy during a previous training session. It is not clear why the vessel had more people on board during this torpedo drill.
“The quality of the navy crew is not in doubt, but the treatment of this submarine may need to be rechecked,” said Connie Rahakundini Bakrie, a military analyst at the University of Indonesia. “I am afraid there is a lack of standard operating procedure maintenance.”
Two Indonesian Navy ships are using sonar to search for the missing vessel, First Admiral Widjojono said. One of the ships was deployed earlier this year to search for the flight recorders of an Indonesian jet that crashed in January.
Navies from neighboring nations, like Australia and Singapore, have been alerted and will join the search in the coming days, Indonesia’s Ministry of Defense said.
A country of thousands of inhabited islands, Indonesia is the world’s largest archipelagic nation. Its navy is poorly funded, even as the country has to contend with regular incursions by foreign fishing fleets and coast guards.
Submarine accidents are rare. In 2000, a Russian Navy submarine sank to the seabed after an explosion on board. All 118 people died after rescue teams took days to gain access to the submarine, and oxygen ran out for the 23 sailors who had survived the blast.
In 2017, an Argentine Navy submarine went missing with 44 people on board, after what was thought to be an electrical malfunction. Its wreckage was found a year later.
But miraculous rescues have occurred. In 2005, seven sailors on board a small Russian Navy submarine that was trapped in a fishing net were freed just a few hours before their oxygen would have run out.
“Crossing my fingers that help from Australia and other countries will come,” said Ms. Bakrie, the Indonesian military analyst, referring to the search for the missing Indonesian submarine. “Crossing my fingers that the crew will all survive.”