Sandra Bullock got up, close and personal with Channing Tatum while filming “The Lost City”.

The actress chatted to Stephen Colbert on Monday’s  “The Late Show”, joking that her co-star was “stupid naked in this film.”

Colbert mentioned that Tatum dropped his trousers entirely at one point to check for leeches, adding that viewers got a “full on shot of his butt.”

READ MORE: Sandra Bullock Talks Stepping Back From Acting, Filming ‘Lost City’ With Channing Tatum

As the host explained how Bullock then had to check his front, he asked: “Was that CGI?”

Bullock responded: “No. [I’m] fully there. Full on face to face, with the, uh… landscape.

“I had to spend some time down there, just making sure no leeches, and I had a lot to say to it. When you’re down there, you may as well just get to know it.”

READ MORE: Sandra Bullock Praises Brad Pitt For Working A Free Extra Day On ‘The Lost City’ Because ‘He’s Just Freaking Awesome’

As Colbert said Bullock’s character Loretta Sage seemed surprised while down there, the star laughed that it could have been that Tatum’s Alan was generously endowed… or not.

Bullock went on, “When you’re down there and you have two pages of dialogue, if you are looking directly at it, you will get nothing done.

“So I looked at his left thigh. I focused more on the left inner thigh.”

“The Late Show with Stephen Colbert” airs weeknights at 11:35 p.m. on Global.