Indonesia is currently searching for a submarine which went missing on Wednesday during a military exercise.
Made in the 1970s, the German-made submarine had 53 people on board when it went missing off the coast of Bali during a torpedo drill.
Indonesian authorities have said the vessel is believed to be 700 meters underwater but is only designed to withstand depths of around 250 to 500 meters.
They added that an oil spill was spotted during aerial surveillance near the dive point and is "highly suspected" to have come from the vessel.
Nearby countries, including Australia, India and Singapore have offered to provide assistance.
South Korea's military also said it is ready to help when needed.