Mystery in the deep blue sea

The honeymoon bride had drowned diving Australia’s Great Barrier Reef.

And before the authorities there, the Queensland police, could issue a finding of "accidental death," they needed to know more about why the story of the dead woman's dive-buddy, her husband of 11 days, was coming up inconsistent.

They'd taken statements from dozens of people who'd heard the husband Gabe Watson recount how he'd lost his wife that morning, forced to adjust his mask and regulator, only to see her drop helplessly to the ocean floor 100 feet down.

It was a kaleidoscope of differing accounts, according to the cops.

Dennis Murphy, Dateline NBC: How many different versions has he told so far of what happened underwater?

Sgt. Brad Flynn: With the interviews that I've done and the interviews that the Queensland police have done, approximately 16.

Dennis Murphy: Sixteen different versions?

Sgt. Flynn: With subtle variances.

The detective from a suburban town in Alabama, Sgt. Brad Flynn, found himself working in an official capacity with the Australian authorities as they probed the puzzling death of the local bride.

In addition to interviewing stateside witnesses who'd been on the dive boat that day, he decided he needed to know more about the couple themselves, Gabe and Tina, the young people who'd met as students at the University of Alabama.

Dennis Murphy: How far back do you go?

Brad Flynn: When they started dating. You paint a picture of someone and you paint a picture of the environment they're in.

Dennis Murphy: So you had to find out who Tina was.

Brad Flynn: Never met anybody that did not have just the best things to say about her.

Dennis Murphy: What's the picture that's coming together of him? Who does Gabe turn out to be to you?

Brad Flynn: Different. Very-- a man that likes to be in control, he knows what he wants and he goes after it. Everybody I've talked to has said that, "You know, Gabe does things one way: his way."

The detective learned that Tina's family thought Gabe a cool customer from the very first.

Tommy Thomas: He wasn't as outgoing with us as some of her boyfriends had been in the past. He had been going with her for quite some time, actually, and we had never met them before.

Cindy Thomas: I just flat told her. I said, "I've just got a really bad feeling. I don't like him." And she told me I wasn't giving him a chance. So, I said, OK, I will try to give him a chance. But we need to get to know him better.

Dennis Murphy: So mom doesn't like him. Dad?

Tommy Thomas: I was still trying to keep the peace. Because if this was the guy that Tina was going with, I wanted him to be a part of our family.

Alanda Thomas: Normally, with past boyfriends, you know, they were all about impressing me, knowing how close me and Tina were.

But Tina's kid sister, Alanda, got the distinct feeling that this new guy Gabe wanted her out of the picture.

Alanda Thomas: He had a problem with Tina being around me. Anytime I would be with her, he would be on the phone, I could hear him on the other end and he was not happy.

Dennis Murphy: What was the attraction? Her for him.

Tommy Thomas: She had just broken off a relationship and he was there. And she had, you know, all of her friends getting married. She joked quite a bit about being a bridesmaid.

Alanda Thomas: She felt old, which is really absurd. She could just see herself as an old maid with a bunch of cats. That's what she'd always say.

But best friend Amanda also remembers Tina began falling for the guy who bought her a Kate Spade handbag.

Amanda Phillips: She thought, you know, he was handsome. And, you know, a good guy. She loved his mother. And wanted to be a part of that family. And, you know, they had already accepted her very warmly into their lives.

In the fall of 2002, Tina told her sister that she'd discovered that Gabe had bought her an engagement ring.

And it's the weird business of the engagement ring that the family cites as exhibit a in their argument that Gabe was manipulative and enjoyed messing with Tina.

Alanda Thomas: My sister had gone over to his condo. and seen the jewelry bag sitting on top of the TV. And she had went over to it to look, and he had warned her that if she looked inside that he would take it back. And it stayed there for a good six months. Every time she went over there, she had to look at the bag.

Tommy Thomas: I said, "Tina just tell him to take the ring back. You know, you don't have to put up with that."

Cindy Thomas: This is something she would have never put up with, with anybody else. And I'm like, I don’t understand this. What's going on with my child?

Dennis Murphy: Was she a little embarrassed?

Amanda Phillips: I think she probably was, but she wouldn't have let anybody else know about it, you know? But it was something that ate her up.

It was only after Tina went to Atlanta one weekend to check out the possibility of a different boyfriend altogether that Gabe finally popped the question in April 2003.

Amanda Phillips: She went to see if there was a spark there, to see if there was any interest and, you know, ultimately it turned out there wasn't a spark.

To her friend Amanda, Tina seemed uncharacteristically deflated as she off-handedly spread the news of her engagement.

Amanda Phillips: There wasn't a big phone call. The, like, "Oh, my God, I'm engaged! This is wonderful!” It was, like, "Yeah. He proposed on Sunday.” I got the impression from her that she felt like she was settling.

Alanda Thomas: She told me that she loved him and he made her happy, so I was happy for her. You know, I was worried, too, though.

The detective learned that the wedding was set for that fall of 2003.

Gabe started shopping honeymoon destinations and that meant his non-diving fiancée would have to get herself certified in scuba.

She'd been taking group lessons out at a local quarry.

Alanda Thomas: During the whole course of it, it was never something that she really seemed happy about doing.

She had to be good to go for the Great Barrier Reef.

Craig Cleckler: I told Tina that, "You've really got to do this, Tina, because you want to." And she made the statement, "You don't understand. I have to do this.”

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