Tragic message discovered as married couple disappeared after being left behind while diving

A married couple from America when on a group diving trip in Australia back in 1998, and went missing - they were never found.

Almost 27 years on from that fateful day on 25 January, 1998, the couple have been presumed dead after their bodies were never found.

Tom and Eileen Lonergan, originally from Louisiana, USA, ventured out to the Coral Sea off the northeast coast of Australia for a diving trip when tragedy struck, with the event inspiring 2003 film, Open Water.

The stop was on their way home from a two-year stay teaching for the Peace Corps on the island of Tuvalu, before living in Fiji for another year.

Determined to travel the world before heading home to the US, the pair were known for their love of scuba diving, after Eileen convinced Tom to take the hobby up.

Any diver's dream would be to visit the Great Barrier Reef, and that's exactly what they set out to do.

Ten years on from their marriage, Tom, 34 and Eileen, 28, the more experienced scuba diver, geared up for a trip to the famous coral reef alongside 24 others on a 26-passenger boat called Outer Edge, led by skipper Geoffrey 'Jack' Nairn.

Travelling 60km off the coast to the reef, the group enjoyed themselves before heading back, though it wasn't until later where it was discovered that the headcount conducted wasn't as accurate as first thought.

When they reached the mainland, they noticed that the American couple were missing, as they were never onboard the Outer Edge when it headed home, meaning the couple likely resurfaced to find the boat had left them behind.

As a search ensued in the months following their disappearance, a fisherman found a chilling dive slate 160km out that said: "[Mo]nday Jan 26; 1998 08am.

"To anyone [who] can help us: We have been abandoned on A[gin]court Reef by MV Outer Edge 25 Jan 98 3pm.

"Please help us [come] to rescue us before we die. Help!!!"

There is no evidence to suggest that their lives came to a violent end, like it did in Open Water, in which the couple are depicted as victims of a shark attack.

The couple were unknowingly left stranded at sea (Tom and Eileen Lonergan)

The date on the slate suggested that the couple were alive for at least one day.

Following the incident, the Outer Edge skipper was charged with manslaughter.

This haunting message came months after a widespread air and sea search to find the missing divers, though authorities were not successful in their searches.

After one month, a wetsuit in Eileen's size washed up on the northern Queensland shore with tears to it, which experts suggested could be a result of contact with a coral.

Dive jackets, tanks and one of Eileen's fins followed on the Australian shore.

Skipper Geoffrey 'Jack' Nairn explained that he told a crew member to do the headcount, though the numbers got mixed up as two passengers jumped into the water halfway through.

Nairn was later found not guilty by a jury.

His company pleaded guilty to negligence and went out of business.