On 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. Widjojono stated that a team of divers was searching for the boat.
Janes Defence News also reported that the navy had sent a number of other warships to the area. The governments of Australia, Singapore, and India had responded to Indonesian requests for assistance. On , the Indonesian Navy reported that an oil slick had been observed at multiple locations. Indonesian frigate
Raden Eddy Martadinata had detected movement underwater at a speed of but was unable to obtain enough information to identify the contact before it disappeared. Admiral Yudo Margono, Chief Staff of Indonesian Navy, also reported that an Indonesian naval vessel had detected an object that was magnetic at a depth of . The Indonesian Navy had deployed six additional ships to the area: , , , , and . Yudo Margono also noted on Thursday that three submarines, five airplanes, and 21 warships had been deployed in the search effort. Submarine had also joined the search. , a warship with more powerful sonar equipment, was expected to arrive on . The
Republic of Singapore Navy deployed its submarine rescue vessel, and the
Royal Malaysian Navy sent its respectively, to the scene. 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.
U.S. Department of Defense press secretary
John Kirby stated that the department was sending airborne assets to assist in the search. These included a
Boeing P-8 Poseidon maritime patrol aircraft with one registered as 553. On 23 April, the
Indonesian National Police also sent four police ships equipped with
remotely operated vehicles (ROVs) and sonar devices. Fleet Commander Australia, Rear Admiral
Mark Hammond announced that
HMAS Ballarat and
HMAS Sirius would join the search operation. Other nations, including Germany, France, Russia, Turkey, and Thailand, offered assistance.
Discovery 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. Because the debris was found within of the point of last contact and no other vessels were believed to be in the area, the debris was believed to have come from the submarine, and
Nanggala was declared sunk. Yudo Margono stated that a sonar scan had shown the submarine at a depth of , and its
crush depth was presumed to be . On 25 April 2021, the Indonesian Navy confirmed that the
Nanggala had imploded and that all 53 personnel on board were lost. Underwater scans identified parts of the submarine, including the rudder,
diving plane, anchor, and external parts of the
pressure hull, as well as items such as an MK11
submarine escape suit. The ROV Super Spartan 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. Using a
multibeam echosounder,
KRI Rigel confirmed the final position of
Nanggala at a depth of at the coordinates , roughly from where
Nanggala had dived. ==Analysis==