Tom and Eileen Lonergan, a young American couple from Louisiana, vanished in 1998 after being accidentally left behind by a scuba diving boat in the Coral Sea near Australia’s Great Barrier Reef. During a group dive excursion with the company Outer Edge, the crew failed to conduct a proper headcount, and the boat departed without the Lonergans—leaving them stranded in open water. Their absence wasn’t discovered until two days later when their belongings were found unclaimed on the boat. Despite extensive air and sea searches, the couple was never found, though pieces of their dive gear eventually washed ashore.