Michael Phelps Strips Down to His Tan Lines For ESPN the Magazine's 'Body Issue' (Exclusive Photo)

Photographed by Carlos Serrao for ESPN The Magazine

The Olympic swimmer is back from retirement — and in the buff — as he joins Paralympian Amy Purdy, Venus Williams and U.S. soccer star Omar Gonzalez, who all stripped for the special issue.

Fans are used to seeing Michael Phelps scantily clad in a Speedo swimsuit — but for the 2014 ESPN The Magazine's The Body Issue, the Olympian strips down to his tan lines.

After taking a break from competitive swimming following the 2012 London Summer Olympics, the 29-year-old is back from retirement and more naked than ever.

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Phelps put it all on display when he posed for the sixth annual Body Issue, which has become famous for persuading athletes at the top of their game to pose in the nude. The Hollywood Reporter got a sneak peek of the 18-time Olympic gold medal winner in all his glory.

While he looks like a sculpted Greek god diving into the water off a board, 6'4" Phelps claims he "got fat" in retirement, which prompted him to stop sleeping in until 2 p.m. and get back in the pool. 

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"I got fat and out of shape. It was hard because I had always eaten whatever I wanted whenever I wanted it," he told ESPN. "I would always be like, 'All right, I'll go work out,' and I would never ever go. Sure enough, 25 pounds later, I was still saying the same thing. That was just part of my learning process."

Luckily, it was easy to shift when he put his mind to it. "I got out of the shower one day, and I'm like: 'Wow. What am I doing?' It was all over after that. I lost 25 pounds in probably six weeks — just working out two hours a day, eating healthy. It shed right off."

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Joining Phelps in the most anticipated issue of the year are 22 athletes, including five-time Wimbledon champion Venus Williams, Seattle Seahawks running back Marshawn Lynch, Olympic gold-medal-winning snowboarder Jamie Anderson, Texas Rangers first baseman Prince Fielder, Oklahoma City Thunder forward Serge Ibaka, U.S. World Cup soccer player Omar Gonzalez (who also plays for the Los Angeles Galaxy) and Paralympian and Dancing With the Stars competitor Amy Purdy

Previous sports icons who have stripped for the special issue are New England Patriots tight end Rob Gronkowski, Clippers' Blake Griffin and even PBR star bull Bushwacker.

Watch video of their shoots below, and see the star athletes reveal all when the ESPN The Magazine's The Body Issue hits newsstands on July 11, and all the images will be available online on Tuesday from 9 a.m. ET at ESPN.com/bodyissue. See the six cover stars reveal all here.