Experienced San Diego Diver Dies During New Mexico Cave Exploration

An experienced San Diego diver who was helping with the exploration of the narrow underwater passageways that radiate from a well-known swimming hole in eastern New Mexico has died, authorities confirmed Thursday.

The initial investigation suggests 43-year-old Shane Thompson's death below the Blue Hole, a tourist destination in the community of Santa Rosa, was an accidental drowning.

"He's done literally thousands of operations," good friend Robert Butler told NBC 7. "Anything from running lines to shore in super rough conditions where his entry point was limited, to diving in couple hundred feet of water...When he wasn't working he was diving, when he wasn't diving he was studying about diving or teaching diving."

Police Chief Jude Gallegos said Thompson was among 10 or so people from the ADM Exploration Foundation who were at Blue Hole for a multiple-day exploration. The group had been working on surveying the underwater cave system since 2013.

Thompson dove into Blue Hole on March 26 with another experienced diver, Mike Young, Gallegos said. They planned to have Young enter part of the cave system while Thompson stayed outside in a safety role.

Instead of staying outside, Thompson entered, Gallegos said. "Apparently something went horribly wrong, and he started to panic," the chief said.

The divers were about 160 feet below the surface when the incident happened.

"Whatever he did in his mind was the best solution to what he thought was going to get him out of that situation," Butler explained. "I know the partner he was with was every bit as good as Shane was. I couldn't fathom a brash mistake being made."

It still was unclear Thursday what went wrong. It could be weeks before autopsy results are available, the state Office of the Medical Investigator said.

No more exploration is planned of the underwater cave system at Blue Hole, said Curt Bowen, president of the exploration foundation.

"The cave system below is walled out. That means there is no cave passage left to explore," he said in an email. "We mapped everything we could fit through, and it ended in a tight rock breakdown at a depth of 194 feet."

Because of the extreme environment within the cave system, the city accepted the group's recommendation that the cave system remain off-limits to the public. The divers covered and secured the grate at the bottom of the bell-shaped swimming hole to prevent untrained divers from gaining access.

Family members said Thursday they were struggling with Thompson's death, but they acknowledged that diving was what he loved to do and that he had earned numerous certifications during his lifetime.

"The diving community lost an icon," Butler said. "You wouldn't even know where to start to appreciate how important he was."

A Navy veteran, Thompson began diving at a young age while growing up in the Florida Keys. After earning his first certification, he went to work for an underwater construction company and later started numerous diving businesses that focused on everything from boat maintenance to salvage work and training.

 Last year, Thompson rediscovered the wreckage of the B-36 "Peacemaker" bomber that had crashed in 1952 near Mission Beach. A video posted by Thompson's San Diego-based Advanced Underwater Training business shows his flashlight scanning the engines and other corroded pieces of the plane as he makes his way through the darkness more than 250 feet below the surface.

In New Mexico, the Blue Hole has been an attraction for centuries. Legend has it that outlaw Billy the Kid would take a dip at the swimming hole before heading into Santa Rosa.

The artesian spring, tucked into a rock outcropping, pumps out about 3,000 gallons per minute. The steady flow results in crystal clear conditions that have attracted divers from around the world.

Beyond the grate, Gallegos described the cave system as "a maze -- kind of looks like intestines."

In the coming weeks, Bowen said he plans to complete a three-dimensional map that will illustrate the entire Blue Hole system.

The caves have been sealed off since 1976, when two divers in training died after getting separated from their classmates. New Mexico State Police divers quickly found one of the bodies, but it took several weeks to find the other. In the process, police divers made a crude map of some of the unexplored passages.

At that time, one of the divers descended and found himself at the edge of an underwater cliff. His powerful flashlight wasn't enough to see the cave wall across from him or the bottom, sparking only more curiosity.

In 2013, divers with the ADM Exploration Foundation attempted an expedition, but they had little success getting past the tons of rock the city dumped onto the grate to keep people out.

Divers with the foundation returned in 2015 for more excavation work and were able to reach a depth of 160 feet.  They returned in late March to continue surveying.

Divers from around the region flock to Blue Hole for fun and certification, as it's one of the best diving spots in the American Southwest. About 8,000 dive permits are sold each year.

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