The chilling story behind this photo - the last image of 26-year-old Tina Watson.

It was a mild morning in October when 26-year-old David Gabriel ‘Gabe’ Watson, and his wife of 11 days, Tina Watson, started the dive expedition that had been the part they were most looking forward to of their Australian honeymoon.

The couple, who had met as students at the University of Alabama, had planned a seven-day dive adventure on the Great Barrier Reef and Coral Sea. While Gabe was a highly experienced diver, with a total of 55 dives, Tina had only started diving lessons in the lead up to her honeymoon. By the time the couple entered the water on October 22, 2003, she had only ever completed 11 dives – all in a local quarry.

The first time Gabe and Tina explored the historic SS Yongala shipwreck site, which sits 48 nautical miles southeast of Townsville, they quickly returned to the surface. Gabe said his dive computer was broken, and fixed it on board their tour vessel, Spoilsport. The couple then entered the water for a second time.

What occurred next has been the subject of a five-year investigation, a coronial inquest, and two criminal trials.

Since he completed his final dive with his wife, the Herald Sun reports Gabe Watson has provided 16 different accounts of what happened.

The only clear detail is that within a few minutes, Gabe had returned safely to the surface, and Tina was alone on the ocean floor.

It was during this time that another diver, Gary Stempler, took a photo of his wife, and inadvertently captured Tina in the background.

When dive instructor Wade Singleton saw Tina Watson lying face up on the ocean floor, he quickly brought her to the surface and on to the Jazz II, another dive boat in the vicinity of the Spoilsport. Singleton and another crew member, Uzi Barnai, performed CPR, and together, they spent 40 minutes trying to resuscitate Tina Watson. Curiously, her husband remained on the Spoilsport, and only came near Tina's body after she was dead.

According to Barnai, who testified in an Alabama court in 2012, Gabe Watson made "strange clucking noises" when he first saw his wife's lifeless body. "It didn't look like he was crying," he said.

Singleton said when he rescued Tina, all her equipment was working, and she had two-thirds of a tank of air remaining. He also said it took him just 90 seconds to bring Tina to the surface, yet Gabe took twice as long to travel half the distance on his way up.

Why?

The following day, an autopsy found Tina's cause of death was drowning. Due to the unexpected and unusual circumstances around her death, a coronial inquiry was held in Queensland. Gabe's several conflicting statements were examined, and evidence was submitted that demonstrated his story was at odds with the data recorded on his dive computer.

Other inconsistencies brought forward by police and witnesses included Gabe's ascent rate following his separation from Tina, his previous and recent dive experience, and his actions as a trained rescue diver.

On 24 April 2008, the coroner, David Glasgow, formally charged Gabe Watson. The inquest read: "David Gabriel Watson I formally charge you that on the 22nd day of October 2003 at the site of the historical shipwreck Yongala forty-eight nautical miles south east from the port of Townsville in the state of Queensland, David Gabriel Watson murdered Christina Mae Watson."

In June 2009, after resisting extradition for six months, Gabe Watson faced trial in Australia. It was argued that Gabe was experienced in rescuing divers, yet had let his wife fall to the ocean floor without attempting to retrieve her. He had also told a number of inconsistent stories, none of which matched the account of the only eyewitness. While he was initially charged with murder, Gabe's charge was amended and he was offered a deal. Ultimately, he pleaded, and was found guilty of, manslaughter. He served just 12 months in prison.

At the conclusion of his prison sentence, Gabe was deported to the United States and immediately arrested on murder charges. Prosecutors claimed Gabe had plotted to kill his wife in Alabama, and therefore could serve prison time in his home country. When major testimony was retracted, however, Alabama judge Tommy Nail acquitted Gabe for lack of evidence.

Now, Gabe Watson lives with his second wife, Kim Lewis, in Alabama.

In 2010, as Gabe's prison sentence for manslaughter was nearing its end, and the threat of a criminal trial in the United States was looming, Tina Watson's father, Tommy Thomas, said "there was really no trial in Australia".

He instead described the case as "merely a sentencing hearing in which an 'Agreed Statement of Facts' between his barristers and the DPP were presented to the sentencing judges, leaving out the vast majority of the evidence and practically all of the witness statements, physical evidence..."

He said he hoped Gabe would "one day actually face all of the evidence and answer to it".

Four years later, Tommy Thomas, who fought tirelessly to get justice for his daughter, died of cancer.

At the time, his wife, and Tina's mother, simply said, "he is holding our sweet daughter now".