The 40-year-old star, who is currently appearing in the big screen flick We Are Marshall, loves to strip down and swim naked, he tells Men's Journal in its February issue.
"As for the skinny-dipping," the Wyoming-reared Fox says, "when I was a kid there wasn't a huge delineation in our family between having clothes on or not having clothes on. And the reason I have so much fun doing it now is people are so shocked by it, and, like, 'Oh, my God, Fox just took his clothes off!' "
Expanding on the topic, he says, "But, I mean, just how long ago was it that we were all wandering around in loincloths? I don't know, dude, but I grew up, all the way until I was 22 years old, fricking in locker rooms showering with f---in' 40 other dudes and you're not checking each other's c--- sizes out, you're just walking around like it's no big deal."
For the record, he adds, "And no, I don't take my clothes off all the time because I think I have a huge unit and want to show it off. I do it because it's frickin' funny!"
Besides going au natural, Fox, happily married for the past 14 years, to a former Italian model named Margherita, also spends his time restoring antique cars, betting on horses, fly fishing – and getting rip-roaring drunk, he tells the magazine.
To that end, he admits, "I'm absolutely an instigator. And I definitely know a lot of people who have woken up the next day and gone, 'I can't believe that happened, and it's f---ing Fox's fault.' Well, it's probably the most honest you've been in a while, man."
Though honesty isn't Fox's personal strong suit: "I'm a liar and a cheat and a thief and the ultimate manipulator," he tells the magazine. "You can never believe a f----ing word that comes out of my mouth. I tell lies every day, man."