BANYUWANGI, Indonesia—Indonesia’s navy on Saturday declared its missing submarine had sunk and cracked open after finding items from the vessel over the past two days, apparently ending hope of finding any of the 53 crew members alive. Military chief Hadi Tjahjanto said the presence of an oil slick as well as debris near the site where the submarine last dove Wednesday off the island of Bali were clear proof the KRI Nanggala 402 had sunk. Indonesian officials earlier considered the vessel to be only missing, but said the submarine’s oxygen supply would have run out early Saturday. Navy Chief Yudo Margono told a press conference in Bali, “If it’s an explosion, it will be in pieces. The cracks happened gradually in some parts when it went down from 300 meters to 400 meters to 500 meters. … If there was an explosion, it would be heard by the sonar.” The …