"There was lots and lots of guys hand digging, trying to expose him making sure nobody was going to hurt him or anything with any equipment," one of the rescuers, Rich Elm, told CNN affiliate WNDU.
An hour went by.
"We were really losing hope fast, and we tried to just stay focused," Michigan City firefighter Brad Kreighbaum told CNN affiliate WSBT. "The first two hours was complete misery."
More than three and a half hours later, signs of life.
Nathan was cold and appeared lifeless but had a heartbeat. He was trapped vertically in the sand.
"One minute you're thinking, 'We don't know what we're going to have,' and you're thinking the worst. Then you're hoping for the best," Elm said.
"Once I had a hold of his head," Kreighbaum said, "I was ... just talking to him, you know, just like I would talk to my own son."
'Never heard of anything like this'
Park rangers do not know what caused the hole. Mount Baldy is the tallest moving sand dune in the national lakeshore, according to the National Park Service. Half-buried trees show its shifting nature.
"I've been a park ranger here at Indiana Dunes National Lakeshore since 1991, and I've never heard of anything like this here or at other sand dune parks," Park Ranger Bruce Rowe told WNDU. "It's baffling."
The beach was closed Monday as authorities investigated what caused the sand to give way.