AUSTIN – Mud is about a guy trying to say one step ahead of the law after killing a guy in San Antonio. He camps out on a little island on the Mississippi River, where he cooks up a plan for how he’ll be reunited with his true love.

It’s hard to imagine Matthew McConaughey not playing the part. In fact, it will probably surprise no one to learn that he actually camped out on the island while filming.

“On set, somebody came up and almost whispered, “Matthew’s gonna camp out on the island. He wants a tent. Do you know anyone who has a tent?'” Mud director Jeff Nichols recalled Sunday morning. “And I remembered thinking, ‘This is awesome. … This is the guy. This is the right guy.’ I never camped out on that island.”

Part of what also made McConaughey the right guy is his small-town Texas upbringing. The main characters in Mud are actually a couple of 14-year-old boys who cross paths with Mud while boating up the river. They strike a deal with the fugitive to help him get a boat running that’s stuck in a tree on the island.

It’s the sort of trouble that only rural kids can get into. And McConaughey said he remembered well being a kid and having nothing but time and wide open spaces to explore. And while he never aided a fugitive (at least he didn’t confess to that Sunday morning) he did manage to construct a 13-story treehouse in the tallest oak tree he could find.

He had a certain gleam in his eye as he recounted the summer he spent on the project. He snuck out some wire cutters from his dad’s trailer, broke into a nearby lumberyard, and used those materials to construct his masterpiece.

“At the very end of the summer, after it was done and we were gonna move, I asked dad to come take a walk with me,” McConaughey says. “And I showed him it was 13 stories, and I think he knows I got the wood from over there.”

 “And I thought you were going to say, ‘And it collapsed’,” Nichols chimed in. “You’re quite the engineer.”

After SXSW, Mud will play the Dallas International Film Festival in April.