The gold medallist, 30, was pulled over for speeding in Baltimore, Maryland in October, 2014, and booked after failing a field sobriety test.

He was subsequently charged with driving under the influence, excessive speeding and crossing double lanes, and after the arrest, Phelps revealed he locked himself in his home for four days before realising he was in desperate need of professional help.

"I was in a really dark place... not wanting to be alive anymore," he tells Sports Illustrated magazine. "I look back now... I lived in a bubble for a long time."

Phelps admits checking into a rehabilitation facility was terrifying because he was scared of facing up to his troubles away from his family and friends. He recalls, "Hug-hug, kiss-kiss, turn in my phone and go to my room. It's probably the most afraid I've ever felt in my life."

However, the treatment helped him do more than just conquer his reliance on alcohol: "I wound up uncovering a lot of things about myself that I probably knew, but I didn't want to approach. One of them was that for a long time, I saw myself as the athlete that I was, but not as a human being."

Phelps, who was hit with a six-month suspension from USA Swimming-sanctioned competitions and given a one-year suspended sentence and 18 months probation for the DUI count, is now clean and sober and he insists he's in the best shape of his life as he looks towards competing in the 2016 Olympics.

"(I) haven't had a single sip and will not have a sip," Phelps claims. "My body fat has dropped significantly, and I'm leaner than I've ever been... I'm back to being the little kid who once said anything is possible. You're going to see a different me than you saw in any of the other Olympics."

Last year's (14) arrest was his second in 10 years - in 2004, he was sentenced to 18 months probation after pleading guilty to a charge of driving while impaired in his native Maryland.