Divers call north and central Florida "cave country" - for the dozens of springs and sinkholes that lead to networks of caverns and twisting tunnels, some hundreds of feet deep and miles long.
The caves can be beautiful. Divers have photographed spellbinding images of sun beaming through aquamarine water at a cave's entrance. Other photos show divers trekking through towering limestone formations, as if in another world.
But for all their allure, the caves can be extremely dangerous. Each year, a few divers get lost in the tunnels. In all, nearly 400 people have died in Florida's caves, according to the nonprofit International Underwater Cave Rescue and Recovery, which assists law enforcement in accident investigations.
In November, diving buddies Joseph Hartranft and Yessic Spencer plunged into the green water leading to a labyrinth here known as "Wayne's World" - descending until they reached a tunnel so narrow they had to squeeze through one at a time. In a large room below, an opening led to a maze of caves that stretch beneath busy streets, homes and a hospital.
A day later, they still hadn't come out. Soon Pasco County sheriff's deputies found Hartranft's 1999 Range Rover parked near the cave network's sinkhole entrance. Search divers were summoned for a grim task.
What happened at Wayne's World, and why?
The answers open some of the mysteries of the increasingly popular underground world - the lure of going deeper that many divers feel, the sometimes ad hoc training and regulation for this sport, the community, the science and the unforgiving risks of cave diving.
Wayne's World, formally known as School Sink, lies a short distance into a patch of woods past a sandy street lined with trailer homes. Children's squeals echo from a nearby elementary school playground. The bluish-green water looks like a lagoon in the middle of a forest of Australian pines, oaks and palms.
And yet, this is one of Pasco County's more complex caves, filled with silt and narrow passages. In the world of cave diving, Wayne's World doesn't attract those looking for an underwater Eden.
"It's a popular dive site for a few, maybe, because of its extreme conditions," including low visibility, says Larry Green, training director of the 1,100-member National Association of Cave Divers. "A few people have been able to go in and do a lot of exploration. But it's a very extreme cave for a recreational dive."
The first Florida cave divers began exploring the passages in the 1950s. Some were trained military divers who had left the service; others had befriended British divers who were already traversing underwater caves in the United Kingdom.
Since then, the region has become one of the world's most popular cave diving destinations, second perhaps only to the Yucatan in Mexico. Divers are attracted to the plethora of caves in such a small radius, each unique.
Deaths in the caves soon followed. In 1967, four University of Georgia students who went cave diving over their Christmas break got lost 350 feet in and drowned.
In another tragedy, a 17-year-old scrawled a final message on his tank after getting disoriented in a cave north of Tampa.
"I love you mom, Dad and Christian," it read, according to a newspaper article on the teen's 1987 death.
Even at Wayne's World, a small wreath with fake flowers and a cross marks where a 45-year-old woman who'd been drinking drowned after jumping in for a dip on a summer afternoon.
Despite the deaths, a band of divers - mostly young and middle-aged men - regularly explore the Florida caves. It's a relatively close-knit community, membership earned once you complete advanced cave-diving training classes and get certified. Training and equipment cost about $10,000.
"It's not the kind of sport where you'll find snobs," said Mike Edmonston, a trainer and dive shop owner who was friendly with Hartranft and Spencer. "We're always helping each other out. There's a lot of camaraderie."
Cave diving deaths have been declining since the 1970s, but divers say a new trend is emerging. Before, most of the people who died in caves didn't have training; these days, more and more do. Technological advances are allowing divers to go deeper, farther, faster before they have acquired enough experience to handle the myriad complications that can arise.
Expensive motorized scooters speed them into the deep. So-called "rebreathers" remove exhaled carbon dioxide and add oxygen to recycle air, allowing divers to stay more than a dozen hours under water.
Complacency is the primary problem, said Green, of the cave divers association. "The caves are not killing people. It's the individual divers not following training guidelines."
He said he'll often question divers who have just received their training and quickly move on to advanced dives:
"Does your wife know what you're doing?"
"When I'm finished and I'm home, I'll give you a call," the 52-year-old Hartranft said in a phone call to his wife and two daughters back in Pennsylvania just before the dive. His son, Joseph Jr., was expecting him home near Tampa by midnight.
When Hartranft and Spencer hadn't returned the next morning, his son first called their cell phones and got no answer, then a nearby dive shop, where an employee hadn't heard from them. That's when he called deputies.
A gate with two metal sheets bearing the words "No Trespassing" prevents cars from pulling in to the Wayne's World site, which is owned by the National Speleological Society's Cave Diving Section. Divers must complete 100 safe cave dives after earning their certification before diving the site, among other stringent qualifications aimed at keeping beginners out.
Hartranft's son told police his father and Spencer filled their air tanks at a nearby dive shop, Scuba West. In an interview with a detective, an employee said Spencer called the next day asking for the combination to the gate in order to pick up trash. He didn't mention anything about diving.
With the level of cave diving instruction the men had, they wouldn't have fulfilled the requirements.
"We're unaware of them inquiring to dive there at all," said Jeff Tobey, the scuba shop's owner. "If they were attempting to get permission from us, they wouldn't have got it."
Hartranft didn't fit the profile of a rugged outdoorsman. He'd spent 20 years in the Navy as a cryptologist. According to a diving instructor, Hartranft was certified as a rescue diver in the military. He enjoyed reading and golf and had moved to Florida two years earlier to work for Lockheed Martin. His wife and two youngest daughters stayed in Pennsylvania.
"It was so unlike him to do this," Robin Hartranft said of her husband's foray into diving.
Hartranft quickly immersed himself in the sport. He began taking classes about a year ago and, when his daughters came down from Dallastown, Pa., to spend six weeks with him in the summer, introduced them to diving as well. Then ages 7 and 9, the girls earned miniature diving certificates, and he framed photos of them wearing their equipment.
He'd even started a foundation to help provide equipment to new divers and law enforcement agencies.
One can glean his excitement in an early post on ScubaBoard.com, a message board for divers.
"Love the Florida dive scene and opportunities," Hartranft wrote back in January 2008. "The experience is awesome for a grunting old 51 yo retired Navy guy...seriously, scuba is the best sport I have ever participated in and has opportunities all over the world - living proof that it is never too late to enjoy..."
Edmonston met Hartranft just as he was getting into the sport.
"He wasn't on an ego trip," Edmonston recalled. "He wasn't trying to prove anything. I guess he had quite a stressful life.... He wanted something to decompress."
Spencer was a lieutenant colonel in the Marines who also taught open-water diving. He'd enlisted in the Navy at 18 and graduated from the U.S. Naval Academy five years later. Since then, he'd risen through the ranks, being deployed to Kuwait, Afghanistan and Iraq. More recently, he was working at U.S. Central Command in Tampa.
"I was very proud of him," Yessic Spencer Jr., his father, said.
"He wouldn't normally do things that were risky, that he didn't think he could master," he said. "He was level headed."
While working at Central Command, Spencer, 42, stayed with Hartranft and his son during the week. On weekends, Spencer, who was married with two young children, would go home to Gainesville.
Edmonston and others remember them as regular diving partners. Spencer, because of his experience, led their expeditions. Hartranft seemed to trust him, implicitly.
Robin Hartranft said her husband tried to assure her that Spencer was knowledgeable and would keep them safe.
"Yessic's here, talk to him," she remembers Hartranft saying one day over the phone before the two went on a dive.
"Joe's fine," Spencer told her. "I'm gonna take care of him."
Robin Hartranft said her husband began cave diving a few months before the November day when he and Spencer drove to Wayne's World.
"I'm a little nervous about it," she remembers him saying, but he added that he wanted to do "something out of the ordinary that I would never do."
Cave diving made Robin Hartranft nervous, too.
Divers need to know how to set and follow a guideline so they don't get lost, and what to do if they get tangled in it. They need to know how to handle themselves when silt, kicked up from a fin or tank, turns clear water cloudy, and what combination of gases to breathe at varying depths.
"There's a lot of math, a lot of physics," Edmonston said.
Hartranft had diving certification through Scuba Schools International and had begun a class on cavern diving, a preliminary course where divers stay within sight of a cave's entrance.
Spencer had certification as an advanced open water instructor, meaning he could teach divers in lakes and oceans. He'd finished an introductory cave-diving course, the first in a series of classes the industry recommends.
"He would call periodically on the phone and ask for information on a wide variety of topics," said his instructor, Bert Wilcher. "We had discussed the fact that he wasn't fully cave trained at that point, and he was uncommittal as to whether or not he was going to take the rest of the classes."
In one post in early October on dive site TheDecoStop.com, Spencer expressed frustration at the number of classes required to learn about Trimix, a combination of gases frequently used by cave divers to prevent nitrogen narcosis. The condition, also known as "rapture of the deep," induces a drunken-like state of consciousness when too much nitrogen enters the bloodstream.
"Mike, I admit that I don't understand Trimix," Spencer wrote. "That's why I'm asking the question. Why do we need three different classes to teach us to dive trimix in the 100-150 ft range?"
"I'm not trying to scrimp on training," he'd written in an earlier post. "Just curious if we are trying to make trimix training more like PADI (put another dollar in)?" The acronym is actually for the Professional Association of Diving Instructors.
About three weeks before the accident, Robin Hartranft got a worrisome call from her husband. He was breathing heavily and sounded anxious. Hartranft told her he'd gone diving with someone in Eagle's Nest, a silty cave that's about 300 feet deep in central Florida.
Something had gone wrong, and they'd gotten the bends, or decompression sickness, which occurs when nitrogen forms bubbles in the tissues and bloodstream.
"Oh my God, Joe," she told him. "This is not good for you."
He said his chest hurt and he felt dizzy.
"He sounded horrible," she recalled. "It was the first time I ever heard him anxious about diving."
Edmonston said Hartranft didn't tell him who his partner had been, but one of their tanks failed. To salvage the remaining gas, they had to cut off access to one tank, essentially leaving the diver with half the gas they'd planned.
"I gave him a piece of my mind," Edmonston said. "I told him, 'It's a really bad idea, never do it again. What are you trying to do?'"
When Robin Hartranft spoke with her husband the next day, he told her the incident had been a fluke.
"I'm up here with two kids, and you know, I'm thinking, all right," she said. "I just thought, something happened and everybody's OK now."
Edmonston last spoke with Hartranft about a week before his November dive. Hartranft wanted Edmonston to help him get certification cards to fill up his tanks with more advanced, combination gases that can be used to dive deeper.
Hartranft wanted to dive Wayne's World and Eagle's Nest, Edmonston recalled. He refused to give him the cards.
"I said that he had absolutely no business being in Wayne's World," Edmonston said. "I told him, 'Do not go in there.'"
"His reply was, 'There's no scuba police.'"
The Pasco County Sheriff's Office relies on a corps of trained cave divers when something goes wrong inside the limestone passages.
Paul Heinerth and Brett Hemphill are among the few who know the intricacies of the caves beneath the Wayne's World sinkhole. After getting the call in November, the two strapped on their gear and went over their protocol: They decided which way they'd go once they entered the cave.
They exchanged "Good luck" and dove to about 40 feet, passing fossil formations and branches to where the sinkhole funnels into a narrow passage.
The small opening led to a room, about 45 feet across at its widest point, with a mound of debris in its center. Divers have to go around the hill to get to another side, and portions of the chamber are large enough to fit a small car.
Heinerth and Hemphill immediately spotted Spencer. He had one arm wrapped around the guideline leading divers through the cave. A reel of rope was attached to his hip and about 6 feet of line lay on the floor, Hemphill remembers.
"When I saw Yessic, I was just sad," he said. "He was so close to the entry."
Neither of Spencer's fins were on his feet. One was about 20 feet away, and the other just inside a new passageway.
Hemphill wrapped up Spencer's extra line so he wouldn't get caught himself, and the men followed the direction of Spencer's flippers. They swam about 70 feet through the tunnel before reaching another large room.
Hartranft's body was there, the hood from his wet suit and his mask pushed back. Heinerth grabbed hold of him and Hemphill helped lead them to the surface.
What exactly happened can't be known for certain, but the rescue divers were able to draw some inferences.
Hemphill speculates that Hartranft veered off course and soon realized he wasn't where he was supposed to be. He managed to make it back to the main guideline, but at that point it was probably loose - as the rescue divers had found it. It was also likely difficult to see very far ahead.
Spencer was having trouble with his tanks. Hemphill said Spencer still had some gas in one tank, but that he'd inadvertently isolated half of his air supply. He'd resorted to breathing from a bottle of oxygen, which can be toxic at 42 feet and under extreme stress.
From where he secured himself to the guideline, Spencer would have been able to see the passage where Hartranft was expected to emerge, Hemphill said.
"If he had no concern for Joe, he would certainly have grabbed that bottle and crawled out of the cave," Hemphill said. "He probably turned around or stayed there long enough to pause and look for a dim light, or some sign that Joe was coming."
Those who knew the men struggle with mixed emotions.
Robin Hartranft, whose own father died of cancer when she was a little girl, said now "my girls don't have their dad. He loved them. They loved him. And still love him. I'm just angry that he's not here."
Together the two men left seven children behind, which filled friends in the cave-diving community with sadness - along with frustration that they had bypassed the requirements to dive the site.
"I think the biggest thing is, it made us mad," Edmonston said. "Because it was completely preventable with available training."
"But you can't hold their hands."