Gary Russell was a mile deep in a Kentucky cave, leading a group of geology students on a five-hour tour, when he turned a corner and saw water rushing by where water wasn't supposed to be.

He had no way to communicate with the outside world Thursday afternoon. He had no idea that a flash flood was pouring through the cave's passages toward them, or that dozens of rescuers were already gathering at the entrance to begin a perilous hours-long journey to rescue them.

All he knew was that water wasn't supposed to be this deep in the cave and that meant trouble.

Russell and his group were among 19 people who escaped the flooded Hidden River Cave. They navigated neck-deep water, rushing currents and mud so thick it sucked off the police chief's boot. It was pitch black.

"It was shooting waterfalls out of the ceiling. The walls were thundering, there was so much water moving through it," said David Foster, the executive director of the American Cave Museum at Horse Cave and a guide for 30 years, who rushed into the darkness to help with the rescue. "You just don't know what Mother Nature is capable of. There's only so much cave, and there's way more water."

The group that spent more than six hours inside the cave included Clemson University students, four tour guides and two police officers who got trapped when they tried to rescue the group, Kentucky State Police Trooper B.J. Eaton said.

There was no communication between the stranded cavers and the more than 150 emergency personnel at the scene. Authorities didn't know exactly where the missing cavers were underground, and the only light the group had came from headlamps they wore.

Heavy rains began pouring down hours after the group ventured inside, Foster said. The storm hit earlier and harder than expected, and Foster grew so worried that he decided to call authorities and trek inside to get them.

The cavers were a group of college students from Clemson University in South Carolina on a field trip to explore the water system in the cave. Russell led four of them on what was supposed to be a five-hour trip beginning at 10 a.m., and another guide had a dozen. Until Russell noticed the water, they were unaware of the rising waters threatening to block the cave's entrance, which is the lowest point and first to flood.

Hidden River Cave begins at a sinkhole, 150-feet deep, in the center of downtown Horse Cave.  It has two subterranean rivers that flow more than 100 feet below ground.

As Russell tried to lead his group out, the mist grew so thick it kept fogging up one student's glasses. He could barely see and kept stumbling.

"Just imagine going hiking in the mountains at night during a rainstorm and a mudslide," Russell said. "That's what this feels like. The water was so loud, it was like a jetliner; it was roaring."

Russell and his group were surprised to find the rescuers at the cave's mouth. But the other guide's group was still unaccounted for.

Foster and Police Chief Sean Henry began working their way deeper into the cave. The water was waist high in places and rising. There's only one way out, and they knew they'd have to come back out the way they came in. At one point, Henry said he saw the water closing in behind him and wondered if he'd ever leave. He held his flashlight in one hand and radio in the other, though his radio stopped picking up a signal shortly after they entered.

They could hear nothing over the roar of the water. Foster started to doubt he'd come down the right passage. He said anxiety built like a rock in his stomach. Then they heard it: "We're here. We're OK!" The students had shouted after seeing their flashlights.

The way out was the most precarious, when they had to wade and swim through high water, Foster said. But they all made it through. They emerged about 4:30 p.m. Everyone lost was accounted for and uninjured.

"When they came out of the cave, they were neck-deep in water," Hart County Emergency Management Director Kerry McDaniel said.

"I've never been more happy to see the sunlight," Foster said. "It's such a good feeling when you get around the corner and you see the light, and you know you're going to make it out. What a relief."