A relaxing day on the golf course went south when Mark Mihal a mortgage broker from the St. Louis suburb of Creve Coeur, found himself 18 feet underground on the 14th hole.

Mihal, 43, and his friends were golfing at the Annbriar Golf Course in Waterloo, Ill., a course that Mihal had played several dozen times over the past 10 years, according to the St. Louis Post-Dispatch.

"The first coupled seconds was terrifying," Mihal told ABC's "Good Morning America" today. "The ground didn't look like there was anything there unusual. By the time I got close to it, I was gone."

Russ Nobbe, the general manager of Annbriar, told ABC News Tuesday he'd been standing right outside the pro shop when the golf pro came running outside to tell him that a player had fallen into a sinkhole.

Nobbe said he loaded a rope and a ladder into his golf cart and headed over to the 14 th hole.

Once on the scene, Nobbe said he tuck the ladder down the hole for Mihal to climb up, but Mihal had dislocated his shoulder during the fall and couldn't make his way up the ladder by himself.

His golfing partners stood around stunned, but quickly sprang into action.

"It was one of those things where I don't think we thought about anything except get him out of that hole," Ed Magaletta told "GMA." Magaletta made a sling from his windbreaker and, using the ladder that Nobbe provided, went into the hole and pulled Mihal to safety.

"His playing partners and myself are the ones who got him out of the hole," Nobbe told ABC News.

Golfer Mike Mihal, swallowed by a sinkhole. Image credit: Mike Peters/golfmanna.com/AP Photo

By the time Mihal was out of the hole, police and an ambulance had arrived at the scene, said Nobbe. Mihal is now home, and feeling better.

"He just couldn't have picked worse timing," Philip Moss, a geologist who knows the area well, told ABC News. "[The sinkhole] would have fallen in certainly in the next rain even if he wasn't there."

Waterloo lies within Ozark ecoregion, which includes Missouri, Arkansas, Oklahoma, Illinois, and a small corner of Kansas. It is an area prone to soil collapses, said Moss, who's an expert on sinkholes.

"We are probably one of the worst areas for soil collapses in the Ozark ecoregion," Moss told ABC News.

"A void in the soil bedrock migrates upward over time. Eventually, you wind up with a fairly thin soil point, and then it collapses. It is not uncommon around here, and in fact it has been happening for thousands of years, but you just can't see it until the soil arch breaks though," said Moss.

Moss explained that the sinkholes that occur in the Ozark ecoregion are very different from the sinkholes in Florida, such as the one that recently swallowed Jeff Bush, 36, of Seffner, as he slept in his bed.

Sinkholes in Florida occur rapidly, said Moss, triggered when the water is drained from limestone caves. But sinkholes such as the one Mihal fell into take hundreds or thousands of years to occur.

"This is an extremely freakish case that this little tiny sinkhole managed to collapse while someone was standing there. The odds of that happening are incredibly small. I would say you would have more luck winning the lottery," said Moss.

Annbriar Gold Course is fixing the hole and hopes to have the full course open by next week.

"Safety is our No. 1 concern going forward," said Nobbe.