Ryan Osmun and Jessika McNeill were trapped in frigid water (File)

It was like a scene out of a horror movie: two hikers, alone in the frigid wilderness with no cell reception, suddenly stumbled into a pool of quicksand.

On Saturday, Ryan Osmun, 34, and and Jessika McNeill from Arizona were about three hours into the Subway trail route in Utah's Zion National Park when their scenic walk took a turn. McNeill tripped, landing in quicksand. When Osmun attempted to rescue her, he too became trapped and buried up to his knee.

"There was no chance of moving it at all," Osmun told CBS News. "The sand had surrounded the whole leg, and I couldn't move it."

Quicksand forms when water or air becomes trapped in sand. If exposed to a sudden shock or stress, like the weight of a hiker, it can become unstable. If something - like a limb - is submerged, it is incredibly hard to escape.

"Quicksand is not normally a problem at Zion, but it does happen if conditions are right," said Alyssa Baltrus, a spokeswoman for the park. "We have been unusually wet here this winter. The weather was most likely a contributing factor."

Despite what Hollywood might have you think, a 2005 study by researchers at the University of Amsterdam showed that it is not possible for a person to sink entirely into quicksand, because they are too buoyant. But that doesn't mean it can't be dangerous.

For Osmun, his predicament meant he was trapped in frigid water and exposed to the elements as winter storms hit the region.

Ultimately, McNeill left Osman to go look for help, or at least for a cell signal so she could call 911. "It was the hardest thing I've had to do. Scariest thing, I didn't even know if I would be able to do that hike by myself," she told ABC News. "There was a couple times I thought I might as well just turn back, and we can just be together for the last moments."

"The water was so cold I thought for sure I'd lose my leg because there was no way she was going to be able to get there fast enough to have people come get me out," Osmun told ABC News.

After hiking alone for hours, McNeill was able to call for help, and rangers located her close to the trailhead, according to a news release from Zion National Park that detailed the rescue. A search-and-rescue team immediately set out to look for Osmun, whom they found several hours later. He was not freed from the quicksand until late in the night, forcing rescuers to stay with him as temperatures plummeted and the park received another 4 inches of snow.

One of the rescuers who found Osmun told him he was lucky to be alive.

"He said, 'I'll be honest with you, you should be dead or unconscious right now,' " Osmun recalled to ABC News.

The next day, a helicopter and rescue crew from the Utah Department of Public Safety was dispatched to lift them out, but weather and poor visibility hampered the efforts until a break in the weather allowed the rescue to be completed. He was taken to the hospital and is recovering.