HERNANDO COUNTY - A sign leading to Eagle Nest Sink compares it with the cave-diving equivalent of climbing Mount Everest.
The enormous underground system reaches depths of more than 300 feet and has a main room the size of a football field.
Warnings posted near a dock at the side of the sinkhole say the descent is dangerous and should only be attempted by certified and experienced cave divers using a combination of gas and air in their tanks.
On Christmas Day, Darrin Spivey and his 15-year-old son Dillon Sanchez made it down 233 feet using air alone.
They died on their way back up.
Neither was a certified cave diver.
Sanchez received new diving equipment as a Christmas present and went to Eagle Nest in the Chassahowitzka Wildlife Management Area with his father to test the new gear, according to the Hernando County Sheriff's Office and family members.
Spivey and Sanchez were last seen by hunters suiting up about 11 a.m. Spivey's fiancee, Holly King, called law enforcement about 3 p.m. after not hearing from the divers and finding their car parked near the sinkhole.
The bodies were recovered by a volunteer cave-diving team about 8:30 p.m. Spivey was found at 127 feet, and Sanchez was found at 67 feet.
Spivey was certified to dive but not to dive in caves, according to law enforcement and family. Sanchez was not a certified diver, according to sheriff's spokeswoman Denise Moloney.
Eric Deister, a volunteer rescue diver who helped recover the bodies, said both Spivey and Sanchez had the correct diving gear but were not using the right breathing gas for the deep dive.
At 233 feet, air becomes "toxic" and nitrogen levels make divers feel drunk, Deister said.
At that depth, Deister said, divers need to use the breathing gas called trimix, a combination of helium, nitrogen and oxygen, to counteract the adverse affects from high levels of nitrogen and oxygen.
Nitrogen has a narcotic effect, usually at depths below 100 feet, Deister said.
Trimix uses helium to remove nitrogen from the body, Deister said.
Eagle Nest is a popular spot that draws between 20 to 40 divers a week with its stunning views and deep caverns, Deister said. The main room of the cave, where the divers were found, is about the size of a football field and a continuous safety line leads divers to the surface.
"I can't emphasize training enough," Deister said. "If they had training, they'd probably be with their families today. Nothing down there is worth your life."
Family members were grief-stricken.
"Darrin should never have been in that place," said Chester Spivey Jr., Spivey's father.
Chester Spivey said he believed his son had been diving for at least five years and had dived Eagle Nest Sink before. Chester Spivey remembers warning his son about the spot and telling him "never to go to that place because so many people died there."
Darrin Spivey grew up in Brooksville and attended Central High School, according to his father. Chester Spivey said some of his fondest memories were riding motorcycles and fishing with his son.
"But prison made him tough," Chester Spivey said of his son. "It got to the point where he became a risk taker."
Records show Spivey served more than two years in prison on charges of leaving the scene of a 2009 accident involving the death of a homeless bicyclist, and obstructing an investigation. He also served a three-year sentence in the 1990s on other charges.
Spivey said he's had a strained relationship with his son, but he believed Darrin Spivey was working to turn his life around since being released from prison in 2012.
"I love my son, unconditionally love him," Chester Spivey said. "I just wish I had more time."
Chester Spivey said Darrin was a "super father" to his three children and two step-children. "One thing that stood out with him, he liked to do things with his kids," Spivey said.
Patricia Davis remembered her nephew as a "good father" and "good family man" with a unique laugh.
"It was a laugh and a giggle at the same time, and you couldn't not help but laugh when you heard it. It was hilarious."
Davis, who lives in Texas, said the family is shocked by the accident, even more so that it happened on Christmas Day.
"Don't forget to tell your loved ones how much they're loved and make them feel it," Davis said, quoting from a prayer she posted on Facebook. "Don't let things go unsaid and undone, might not get the chance. It's so true."
Assistant Hernando County Fire Chief Kevin Carroll said the two divers were friends with some of the fire department employees.
"It was very unfortunate," Carroll said. "Our hearts and prayers go out to the family and friends."
The medical examiner's office is still investigating the cause of death, and the sheriff's office continues its investigation.