At the indie drama's premiere Sunday in New York City, the slimmed-down star had this to say when asked about his three kids and Reese's brood playing together when they shot the film in Arkansas in the fall of 2011.
"It was like a nature vacation camping out on the Mississippi River. And we enjoyed it. The kids learned a lot about nature actually on this film," McConaughey told E! News while walking the red carpet.
Now that's livin'.
In Mud, the 43-year-old thesp plays the titular character, a fugitive who befriends two Arkansas teens while trying to reunite with his true love, played by Witherspoon.
The film's release is set for April 26.
—Reporting by Kathy Buccio