Rescue aircrafts and ships scoured the sea north of Bali on Friday, hunting for an Indonesian submarine gone missing along with a 53-person crew.They're racing against an oxygen supply that would have become critically low.Contact was lost on Wednesday with the KRI Nanggala-402 during a torpedo drill.Helicopters flew from Bali at first light on Friday while navy ships were deployed from the neighbouring island of Banyuwangi early in the morning, to the submarine's last known location. Officials have said the air supply onboard would only last until Saturday.One Banyuwangi resident could only hope for the best. "I hope that they can handle this well and quick, and that they can save the whole crew on board."Nothing conclusive has come out of the search so far, though Indonesia's navy Chief of Staff said an item with a 'high magnetic force' had been spotted within a hundred meters from the water's surface. It was unclear if the object was suspended or on the sea floor.Other countries including Australia, Malaysia, India, Singapore and the U.S. have sent ships or aircraft to assist in the search.The 44-year-old vessel in question had been cleared for use and was said to be in good condition. But an aerial search also spotted an oil spill near the submarine's dive location.The navy said that could indicate damage to the vessel, or be a signal from the crew.