On the cult hit show Californication, Jason Beghe played a novelist who had a propensity for stripping off all his clothes whenever he drank. But Beghe says shooting the recurring stunt was no big deal. “I’m naked all the time underneath my clothes, so I’m used to it,” he says. “In fact, I think I was born naked. So it doesn’t bother me.”

It also probably helps that the 57-year-old Beghe has virtually no body fat on his deceptively muscular frame. It was back in high school in New York City (when he would pal around with John F. Kennedy Jr. and David Duchovny) where he took up wrestling and became, as he puts it, “a mesomorphic guy.”

But, amazingly, the actor known for his gravelly voice says he rarely works out in a formal sense. Instead, when he’s not in the Windy City shooting Chicago P.D. (in which he stars as tough-as-nails police sergeant Hank Voight), he stays active on his Malibu ranch. He plays soccer and jumps on the trampoline with his two sons. But he also plants trees, digs holes, mends fences, and bales hay—activities he calls “gardening.”

“Gardening is badass, man!” insists Beghe. “It’s not a half-hour workout. It’s a full day. It’s rough and tough.”

Beghe combines this “gardening” with a diet that includes no soda or fast food. “I like clean, healthy, organic food,” says Beghe. “We have our own fruit and cook our own vegetables at the ranch.”

But the secret to Beghe’s health may be what he drinks. He loves water and tries to consume a gallon a day. “I drink a lot of water,” says Beghe. “It’s so fucking delicious.”

Of course, Beghe also gets a little exercise on Chicago P.D., when he occasionally has to wail on a suspect. In fact, he once tore his biceps tendon while flipping another actor off a gurney. He had to wear a sling for a while, but he continued working. “As long as I can keep putting breath on a mirror,” says Beghe, “I’ll show up.”

Tune in: The season finale of Chicago P.D. airs May 17 at 10 p.m. EST on NBC.