Summer is usually the slow season for scuba diving at Bonne Terre Mine in Missouri, about an hour south of St. Louis. But not this year. Not since 12 young soccer players and their coach were rescued from a flooded cave in Mae Sai, Thailand, captivating the world and thrusting diving into the spotlight.

“My gosh our phone’s been blowing up, it’s been great,” said Douglas Goergens, who owns the mine with his wife, Catherine.

He said the calls started coming in one week into the two-week ordeal and continued through the rescue, with people inquiring about diving and diving certification — and wanting to talk about what they were seeing in Northern Thailand. “It’s shown how diving can actually save people’s lives who are not divers,” Goergens said. “Had it turned out bad, I don’t know, but my gosh, the way it turned out, it’s a miracle.”

Bonne Terre is a former lead mine that plunges 500 feet below the surface. It operated for about 100 years, starting in 1860. When it was a working mine, groundwater was pumped out; when the mining stopped, so did the pumps, submerging three of the mine’s five levels and, in essence, stopping time.

“It preserved all this history,” Goergens said. “We’ve got over 100-year-old ore carts, the rail systems, the buildings. We’ve got an area called ‘the City.’ There’s even an old cast-iron drinking fountain outside one of our offices underwater. There’s a movie theater, there’s a lunch room, there’s machine shops, there’s geology labs.”

Divers with open-water certification can take 50 trails to explore what Goergens calls the world’s largest man-made underground caverns. The Goergens operate West End Diving, which trains people to dive, and walking and boating tours are also available. After Thailand, Douglas expects that more people will be interested in trying diving.

Open-water certification is just the beginning for people who wish to venture deeper into the realm of cavern and cave diving. That type of diving is highly technical, and divers need rigorous experience and training.

Although it’s only been a matter of weeks since the start of the Thailand cave incident, the Professional Association of Diving Instructors (PADI), which is the world’s leading scuba training organization, has seen increased demand: Global PADI Cavern Diver certifications have increased 150 percent over this month last year, according to the organization. Before enrolling in those courses, divers need to be at least 18 years old and be certified as a PADI Advanced Open Water Diver. The main difference between cavern and cave diving, according to PADI, is that with cavern diving the diver will always be able to see natural light, making it easy to access open water.

Drew Richardson, president and CEO of PADI Worldwide, said the increased interest is natural, given the recent drama.

“The world watched as the Thai government, Thai military, the global elite of the cave-diving community and other international experts executed the heroic rescue of 12 boys and their coach,” he says. “This selfless team effort makes me proud of the diving community PADI serves. It’s the kind of thing that makes people want to take part.”

Aspiring cave divers should expect to put a lot of time and energy into training for the endeavor, said Rick Murcar, a cave-diving instructor in Zephyrhills, Fla.

Murcar, who owns Aquatic Adventures and Genesis Diving Institute of Florida, said that he, too, has received an increase in calls. As the president of the National Association for Cave Diving, Murcar is quick to add that he doesn’t encourage people to get into cave diving. That’s something they must decide for themselves.

“My first question to them is ‘Why?’ ” he said. “We talk with the student, assessing their intentions and motives.”

That’s important because of the danger involved with cave diving. In Thailand, a volunteer diver and retired Thai navy SEAL died during the rescue effort when he ran out of oxygen. It’s a possibility that every prospective cave diver must consider, Murcar said. “Each student of cave diving is viewed as the next possible cave diving fatality,” he said.

Rob McGann, a cave-diving guide and instructor in O’Brien, Fla., leads advanced divers through the cave systems in North Florida. He says he loves the complex planning required for cave diving, as well as the serenity.

“There’s beautiful rock formations and clay banks that you can see underwater that have not been touched for thousands of years,” McGann said. To get to that point, he emphasized, requires dedication and determination. “Generally speaking, it takes about five years for somebody to go through open water and then to get the skills needed for cave diving,” he said.

For divers who don’t want to venture down such a deep path, there’s a former Missouri lead mine where stadium lighting shines down from above and visibility is always about 100 feet — not to mention quarries, lakes and other waterways around the world — ready to be explored.

Silver is a writer based in Chicago. Find her on Twitter: @K8Silver.

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