Greg Louganis was among the biggest sports stars of the 1980s, winning gold medals in both platform and springboard diving in both the 1984 and 1988 Olympic Games.

But he never fully cashed in on marketing that stardom, in part because of rumors that he was gay, something he later confirmed publicly, along with the fact he is HIV positive.

HBO looks back at all of that, and what Louganis' life is like today, in "Back on Board," a documentary that premieres at 10 p.m. Tuesday. At 55, he has become a vocal advocate for LGBT causes.

DatabaseU.S. Olympic medal history

"I am so thrilled, honored and humbled; this film has the power to saves," Louganis said after a screening in Manhattan.

The first time he saw the film, he said, "It was a little awkward, because I was seeming to make the same mistakes over and over again and that's a little embarrassing. When am I going to learn this lesson? You're going to learn it when you're ready to learn it."

Louganis is seen in the film in recent years dealing with financial problems, including the threat of losing his longtime California home.

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He said he trusted director Cheryl Furjanic with telling his tale, flaws and all.

"After spending so much time with Cheryl I knew that the story would be told with love and compassion and so I had absolutely no reservations in trusting them," he said.

Among those in attendance at the screening Tuesday were Louganis' husband, Johnny Chaillot, famed playwright and LGBT rights activist Larry Kramer, and Mallory Hagan, Miss America of 2013.

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"Within a couple of days of winning the Miss New York competition back in 2012, Greg and I did this July 4 event out in Coney Island," Hagan said. "We did the whole Nathan's Hot Dog Day. I was getting ready for Miss America. I was not in the hot-dog eating contest. We actually were in this 15-foot apple pie dive where we were diving for charity.

"It was me and Greg and a couple of other people . . . Long story short, Johnny, his husband, and I sort of fell in love. We've stayed in touch ever since and I lived in Los Angeles for a little bit so we spent time together there.

"They're kind of like having two awesome uncles."

Hagan, 26, said before the screening that she did not know much about Louganis' diving career.

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"For as much time as I've spent with them, it's been so in the present and not in the past, so I'm really interested to see the documentary and see what these last three years of his life have been like and to really learn about him as an individual before we met," she said.

Hagan said she is using her Miss America scholarship money to finish her education at the Fashion Institute of Technology.

"I'm studying advertising, marketing and communications," she said. "And I'm looking for a job, if anyone is hiring."