Channing Tatum Faces Impossible Test in a Freezing River on NatGeo's 'Running Wild' (Exclusive)

ET exclusively debuts a first look from Tuesday's episode.

Channing Tatum is testing his will.

Five years since the Magic Mike star first appeared on Running Wild With Bear Grylls, the 39-year-old actor is back for his second round of intense survivalist training with host Bear Grylls and only ET has the exclusive first look from the episode.

Tatum's first go-around featured a whirlwind 48 hours in Yosemite National Park in Northern California, which culminated in Tatum propelling down a steep cliff. Now, Tatum ventures overseas to Gloppedalsura, Norway, where he and Grylls skydive into brutal terrain and embark on a seven-mile trek, where Grylls puts Tatum through Navy SEAL training to see how far he's come as a survivalist.

In ET's exclusive clip, Tatum prepares to endure three minutes of wading through an ice-cold river to see if he can pass muster as a Navy SEAL through cold-water immersion training and to see if he can remain calm, think under pressure and still remember key things. To say his nerves are on another level, though, is the understatement of the year.

"We're going to tread water for three minutes and then get out and then I have to use my brain afterwards which will be completely frozen, shut down," he says, nervously anticipating completing the task. "I have no idea if I'm going to be able to do this or not because I know when you get really cold, I know that your brain can sometimes not function"

"My brain sometimes just doesn't function when it's completely fine and nice and warm," Tatum deadpans, as he throws off his jacket and follows Grylls into the freezing Norwegian river in nothing but a T-shirt(!) and jeans -- hot ember in hand. As he wades deeper into the water, Tatum begins questioning his choice to go through with this impossible task.

"It was definitely cold. As soon as you get in, you're like, 'I'm not sure 'm going to be able to do this!'" Tatum admits. "Usually in these moments on movie sets, they call in a stunt guy and I always feel emasculated so I'm happy that there's no stunt guy. So at the end of everything, I can just kind of just be like -- whether it was a success or a failure -- it was my failure or success."

Does he successfully complete the test? Watch ET's exclusive sneak peek above to find out. 

A new episode of Running Wild With Bear Grylls airs Tuesday, Dec. 17 at 10 p.m. ET/PT on NatGeo.

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