Alistair Donohoe is a man consumed with Paralympic gold — boldly unafraid to declare his ambitions, but tortured by past failures. 

Melissa Wu is defying history at 32, aiming for a record fifth Olympics, continuing an exceptional elite career which started when she was just a child. 

Noemie Fox is on a seemingly impossible journey to navigate one of the toughest qualification pathways in any sport, to join the rest of her family as an Olympian. 

Campbell Harrison wants to create a more inclusive sporting environment for all, especially queer athletes, and is using sport climbing to lead the way. 

And Jamieson Leeson never thought she'd ever be able to participate in sport — now she's a Paralympic gold medal favourite. 

These athletes share all in ABC Sport's new documentary, Countdown to Paris.

Alistair Donohoe's scar tissue

Alistair Donohoe was within reach of gold at the Rio 2016 Paralympics, and it's something which haunts him constantly. 

Donohoe was in a sprint finish in the road race, and well placed to edge out Ukranian competitior Yehor Dementyev. 

But Dementyev clipped Donohoe's bike, sending both men crashing and the Australian desperately running to the finish line.

"But my bike didn't cross, so I didn't win," Donohoe says.  

"That definitely put an emotional setback on me because I put so much energy and time and investment into winning this gold medal, I cared so much about it. 

"And then it literally got ripped away from me.

"Unfortunately it's kind of scary coming towards Paris. If I don't win it, it's going to f***ing hurt. And I'm just going to have to prepare myself that might be the outcome."

Noemie Fox's family ties

Expectation used to overwhelm Noemie Fox, now she's embracing it.  

Canoe slalom has been a dominant presence throughout her entire life, with parents Myriam and Richard, and sister Jessica, all Olympians. 

Jess also happens to be the most successful paddler in history, and has previously blocked Noemie's hopes of competing at the Olympics, taking Australia's only available quota positions.

"Having a sister that is the GOAT in our sport, so the greatest of all time, comes with its challenges and advantages," Fox says.

"When I was growing up, it was much harder not having that sense of identity or constantly comparing and then having extended family members being like, 'oh, you do the sport too?'"

But for the first time Noemie had an Olympic opening with an additional quota position available in the new discipline of kayak cross. 

To get it, she had to finish in the top three athletes at the global qualification event in Prague. 

"It's so incredible to be able to fully commit to something and see where that takes you and say, well, at least I gave it everything," she says.

"I'd rather be shattered and heartbroken and there'll only be good things that came from it, the strength, that mental focus, mental resilience."

Melissa Wu's historic quest

For the past two decades Melissa Wu's life has centred on elite diving. 

Her first major international competition came as a 13-year-old at the 2006 Melbourne Commonwealth Games, and an Olympic debut two years later. 

She decided to give history a shake, and become the first Australian diver to contest five Olympics. 

"It's the first time in my career I've just really dived for me and with not as much pressure, just enjoying it," she says.

"After Tokyo, finally having won that [bronze] medal, I could take a bit of a breath and be like, OK we've done it now.

"Even though I enjoyed that journey, that process definitely took a bit of a toll mentally and physically. 

"But now I look at it as bonus time."

Campbell Harrison's trailblazing path

Campbell Harrison is a sport climber, and the benefit of being in one of the newest Olympic sports is the ability to help shape its culture, as a member of the International Federation of Sport Climbing Athletes' Commission.

"Older, more traditional sports like AFL in Australia, there's this assumption that it's very masculine, it's these macho characteristics of strength and power and aggression," he says.

"And I think that can be quite scary and intimidating, especially to women and also to young queer people who are so accustomed to keeping out of the limelight.

"Especially those of us who felt like being queer was a secret that we had to hide, at risk to our safety and wellbeing. 

"Putting yourself out there in that kind of sporting environment doesn't really feel like a safe place for people who are a little bit different. 

"And I think those of us who exist in younger, newer sports like climbing, for instance, have this really unique opportunity to build in a positive culture from the grassroots. 

"We have this almost blank slate upon which we can build our sport and instil these values."

Jamieson Leeson's life changing moment

Jamieson Leeson wasn't interested in playing boccia when it was first introduced to her while at school. 

"Growing up in the small country town of Dunedoo in New South Wales, with such a significant physical disability, there wasn't many sports, if any, available for me," Leeson says.

"So for the majority of my childhood, was spent sitting on the sidelines cheering on my friends and my siblings in whatever sport they were doing, and I was the biggest fan of sport."

After some initial resistance, Leeson's participation in boccia, one of the few sports available for people with severe disabilities, has turned into a life changing career, where she's now part of the world number one BC3 pairs team alongside Dan Michel.

"It's given me so much more to my life that I didn't have before and taken me and given me so many opportunities that I never knew I could even have," she says.

Countdown to Paris is available to watch above, or on ABC iview and ABC News In-Depth on YouTube.