Disappearance of Tom and Eileen Lonergan

Thomas Joseph Lonergan (born 28 December 1964) and Eileen Cassidy Lonergan (née Hains; born 3 March 1969) were an American couple who were abandoned in the Coral Sea off Australia's northeast coast on 25 January 1998 during a group scuba-diving trip aboard MV Outer Edge. The boat crew did not note their absences until two days later, on 27 January. While search efforts resulted in the discovery of personal effects presumed to be those of the Lonergans, the discoveries did not lead to their rescue. Neither has been found, and both are presumed dead.

The couple's disappearance and deaths resulted in "a crisis of confidence in north Queensland's dive industry" and resulted in tighter mandatory safety regulations for diving boats in Australia. Their disappearances also served as the inspiration for the 2003 film Open Water.