Ben McDaniel

On some nights when they had seen Ben dive late, the two had stayed at the spring after resurfacing until they saw bubbles on the surface, indicating that he was beginning to decompress in order to safely resurface. But on the night of the 18th, they instead went back to Taran's house for coffee.

Ben's dives at the site were regular enough that the dive shop employees and other frequent visitors came to know him. One of the employees, Chuck Cronin, believed that while Ben had the proper equipment and considerable diving knowledge, he was often overly confident in his abilities and not shy about saying so. That opinion, the Memphis Commercial Appeal later reported, was shared by posters on a scuba diving website, scubaboard.com, who had also met Ben during trips to Vortex Spring. (According to a 2014 online comment by his father, he could not find anyone at Vortex Spring willing to be his diving partner, so he did his dives alone.) His parents later defended him from those criticisms by seeing them as positive traits. "Ben was brave," his father later said. "Ben was fearless. He followed his passions."

In mid-August, four months into his Florida sojourn, Ben returned to Tennessee for a week. His parents and girlfriend, Emily Greer, said he seemed optimistic. He told them he was working on getting certified as an instructor so he could find a job and that he was researching cave diving with an eye toward getting that certification as well. On his nights out with Greer, he told her of plans to eventually start a diving-related business. On the weekend of August 14–15, he returned to Florida, leaving behind a letter thanking his parents for the sabbatical and promising to look after them as they grew older. They never saw him again.

Cronin and fellow employee Eduardo Taran, on their way back from a dive themselves – something they often did on Wednesdays after the shop closed – saw Ben as he began descending, with his lights on and wearing a helmet, suggesting he was venturing into the cave. Taran, who had suspected for some time that Ben was forcing the gate open, went down to him and unlocked it, watching Ben go in and then returning to Cronin. No one is known to have seen him since.

Sorenson, who has been described by the Tampa Bay Times as being able to go where other divers cannot, persisted. He made three separate dives that day, going (by his account) 1,700 feet (520 m) into the cave, 200 feet (61 m) further than those sections Ben had mapped, using a diver propulsion vehicle and smaller tanks to increase his range. He found nothing – no body, and no evidence of one such as increased activity by carnivorous aquatic scavengers, nor any evidence that Ben had gotten into those sections, such as marks on the cave walls or disturbed silt.

McDaniel had been living at his parents' beach house on the Emerald Coast during what they called a "sabbatical" in the wake of a divorce, a business failure, and the death of his younger brother two years earlier. An avid diver since his teens, he had been a regular at the spring, where he had apparently been covertly exploring the cave despite lacking the required certification. Lengthy searches have only located some anomalously placed and filled decompression tanks; many of the divers who took part in those searches believe that if McDaniel is indeed dead, his body is not in the cave as he was too large to enter its narrower passages. The McDaniels devoted their family's extensive financial resources to the search, at one point guaranteeing the replacement cost of a remotely operated underwater vehicle (ROV). A reward they offered was rescinded in 2012 after the death of another diver who may have been trying to collect it, vindicating the criticism of the divers who had warned of that possibility and resented the McDaniels' insinuation that those who had searched for their son at great personal risk had not been "brave" enough.

In March 2012, by which time the reward had been increased to $30,000, the fears of the cave divers were realized. Two days before the Investigation Discovery cable channel series Disappeared aired a segment on Ben's case, a diver from Biloxi, Mississippi, Larry Higginbotham, died in the cavern at Vortex Spring. His body was found the next day after he, too, had failed to return from a dive. "He just got himself in a pinch and couldn't find his way back out", said one of the divers who recovered the body.

She and McClellan turned their private video short into a feature-length documentary, Ben's Vortex, released in 2012. It considers all the theories regarding its subject's disappearance: an accident as originally believed, a murder or coverup of the accident as the McDaniels have sometimes alleged, and the possibility of a staged disappearance to allow Ben to escape his problems, which McClellan believes.

Although the McDaniels continue to believe Ben's body is in an area of the cave beyond the reach of current search capabilities, they have also entertained the possibility that his death was not an accident but the result of foul play. A private investigator they hired believes that his body may have been removed before any authorities were contacted, or that he may even have been murdered on land and the narrative of his disappearance fabricated as a cover story. The family believes that the suspicious, supposedly accidental, death of Vortex Spring's owner Lowell Kelly late in 2011 is related to the case. They have also criticized the local police investigation as inadequate, particularly a lie detector test passed by the employee who was the last person known to have seen Ben alive.

In 2011 Kelly disposed of the charges against him by pleading no contest. In return he was fined and sentenced to seven years of probation. He did not live long enough to complete even one of those years.

In 2011, with it looking unlikely that Ben's body would be found in the cave, the McDaniels began considering the possibility that he had died not in a diving accident but as a result of foul play, and that the disappearance might have been staged to cover that up (or at the very least he had been found dead by the dive shop staff, who feared the consequences of that discovery). They hired a Florida private investigator, Lynn-Marie Carty, who found that other people associated with Vortex Spring besides Kelly had criminal records. "There is just as much reason to look above the water for Ben's body as there was to look below it in the cave," she told the Commercial Appeal.

On August 20, 2010, employees in the dive shop at Vortex Spring, north of Ponce de Leon, Florida, United States, noticed that a pickup truck had remained in the shop's parking lot for the previous two days. It belonged to Ben McDaniel (born April 15, 1980), a Tennesseean who had been diving regularly at the spring while living in his parents' nearby beach house. He had last been seen by two of those employees on the evening of August 18, on a dive entering a cave 58 feet (18 m) below the water's surface. While he was initially believed to have drowned on that dive, and his parents still strongly believe his body is in an inaccessible reach of the extensive cave system, no trace of him has ever been found. Despite this, the state of Florida issued his family a death certificate in 2013.

The McDaniels suggested their son take a sabbatical, offering to support him financially while he and his dog, a chocolate Labrador he had rescued, lived in the family's beach home at Santa Rosa Beach on the Emerald Coast of the Florida Panhandle. He accepted the offer and moved into the house in April 2010. His parents and girlfriend say the move was proving beneficial, as Ben was beginning to think and talk about moving on from his recent personal setbacks.

Frustrated by the limitations the search had thus far encountered, and increasingly coming to believe that Ben's body was in an area of the cave no one had yet reached, the McDaniels offered a reward of $10,000, raised from money contributed at a benefit held on what would have been their son's 31st birthday, at the end of the year to anyone "brave" enough to go to those places and find it. The insinuation of cowardice alienated divers who had already risked their lives searching the cave, and raised fears among them that it would only encourage untrained divers to enter the cave and take potentially fatal risks for the reward money. Undeterred, the McDaniels increased the award, twice.

The McDaniels did what they could to help the search. They hired Steve Keene, who had originally mapped the Vortex Spring cave in 2003, to look. After seven dives, he apologized to the McDaniels for not finding any fresh sign of Ben. "If he's in there, I don't know where he'd be," he said later. They agreed to put up $54,000 to guarantee the cost of replacing a remotely operated underwater vehicle brought to the spring by the Fort Lauderdale police, in case it was lost in the cave. (Due to technical issues, it was unable to go any farther than the human divers had ventured.) In total, 16 divers spent 36 straight days looking for Ben's body in the cave with no results. Volunteer searches continued afterwards at the spring through November, often with the McDaniels and Greer in attendance.

In the late 2000s Ben McDaniel was going through a difficult period in his life. The oldest of three sons born to Shelby and Patty McDaniel, a wealthy couple who lived in Collierville, Tennessee, outside Memphis, he had returned to live with his parents after his marriage ended in divorce and his construction business failed, the latter leaving him with tax debts of almost $50,000 to the Internal Revenue Service and the state of Tennessee. He was also still grieving for his younger brother Paul, a frequent rock climbing partner during their youth, who died in 2008 at the age of 22 from a stroke. Ben had found Paul unconscious in the family home and tried to revive him; he later became active in raising money for the foundation his parents established to support research into prevention and treatment of strokes.

For the most experienced divers, some of whom come from around the world, the main attraction of Vortex Spring is the cave, which starts 300 feet (91 m) from the cavern, at a depth of 115 feet (35 m). At the entrance is a sign depicting the Grim Reaper and warning divers that the consequences of continuing past that point could be fatal. The cave continues, steadily narrowing, to a locked gate almost 300 feet (91 m) from the entrance. The dive shop gives the key only to those who can show that they have cave diving certification, which requires two months' training including 125 dives with an instructor or certified diving partner. This policy was instituted after the deaths of 13 divers in the cave during the 1990s, in response to threats from the state to ban diving in the cave entirely. Starting from the gate, over 1,600 feet (490 m) through the area's limestone bedrock have been mapped, to a depth of 310 feet (94 m); the cave's full extent is not known. At some points the passage narrows to 10 inches (25 cm), requiring divers who would pass through to take off their tanks and hold them at their sides or in front, and twist their bodies.