Australian swimmer Dan Smith made an incredible recovery from a drug addiction which saw him made homeless and turn to crime before going on to compete in the Rio Olympics this summer.

Smith and his teammates came fourth in the 4x200m freestyle relay – a disappointing result after winning bronze at the world championships last year, but one which Smith says has forced him to rely on his Christian faith.

"It's taught me a lot – to be grateful and to appreciate I'm here, I'm alive, I'm healthy and I'm fit, I'm living a good life. So for me, that's what the Lord's really been doing in me," he told sports media organisation Passion for Sport.

Disappointing result aside, 25-year-old Smith's return to the water has been called a "comeback fairytale". After swimming success as a child, he turned to alcohol as a teenager which resulted in him having a drink-driving accident aged 18, just four weeks after winning his first open Australian title.

"All that kind of stuff that the world throws at you... I thought that was the answer to life," he says. "I'm up there with the top best athletes in Australia – I was fast and I was starting to swim well, but my personal life just got the best of me."

Smith recalls not knowing "how to deal with all the shame, the guilt, the embarrassment" of his accident, and describes himself as "a very empty, lost and broken boy. I had anger problems, anxiety and all that kind of stuff, I hated the limelight. And so for me the best way I knew how to deal with it was to start smoking marijuana and getting into more drinking.

"Life really just swept me off my feet. I thought I would be OK, I'd just use a little bit of drugs here and everything would be alright, but really it literally destroyed my life."

Smith ended up with an addition to crystal meth, known colloquially as ice. The first time he tried it, a man told him he'd lose everything within three months. "Within one month, I kid you not, I'd lost absolutely everything," he says.

He turned to crime to fund his habit, and ended up living on the streets after his family kicked him out. "It really destroyed my family," he says. "I've seen the hurt that I've put them through. You can imagine what it would be like watching your son that you love so much... he's Australian champion, should be at the Olympics, and now he's living on the street an ice addict. It would break anyone's heart, watching that."

Eventually, after finding out about some health issues, Smith became suicidal. He credits his faith with pulling him back from the brink.

"I'm a Christian, I do believe, because I've literally had more lives now than a cat. I've been through literally hell and back, God's hand's just been upon my life the whole time. I can't deny it any more," he says.

"I've always pushed the boundaries and stuff, but I'm a complete new person now and that's what the Lord's done in my life. He's made me a new person and I'm extremely grateful to him for what he's done in me."

Smith added that he "used to live in turmoil" but he has found peace with God. His addiction to drugs, he says, was an attempt to "fill [a] void, and that's what He's done – He's filled me from the inside out."

But the biggest change, Smith says, is that God has "really been working on my character.

"When I became a Christian I came back to the sport. I was like, 'Jesus walked on water, I'm supernatural now, I can do anything I want to do'. But for me swimming hasn't really happened like that. I've had to really work on my character, and be satisfied and know that gold medals and winning and all that kind of stuff isn't who you are. Swimming is just what I do, and for me it's taken me a long time to realise that revelation.

"Swimming isn't who I am it's just what I do. I'm a vessel of the Holy Spirit, God loves me – it's taken me a bit of time to really realise that. God doesn't need gold medals and stuff, he cares more about my character and what's on the inside."

Looking ahead to Tokyo 2020, Smith is optimistic. "With the Lord, I guess the sky's the limit with my Olympic journey and my swimming," he says. "I'm just more driven than ever, more focussed, and I'm just really excited about my future now."