Cave diving is fraught with danger, but the reward is sights like nothing else on Earth

The light fades as divers disappear deeper into a cave system, until the greenish tint of flashlights appears, bouncing off walls, picking out creatures people may have never seen before, and illuminating a world otherwise trapped in pitch black.

These caverns can extend for hundreds of miles into dangerous, otherworldly mazes unlike any other place on Earth.

Any cave diver is well aware of the dangers involved in exploring these unfamiliar territories. Experienced Canadian cave diver Jill Heinerth recalls in the 2024 documentary “Dive into the Dark” that “I was always swimming in the graves of my friends. This list consists of well over a hundred people.”

The dangers of this highly specialized discipline have been highlighted once again this month. Five Italian divers died While exploring the caves of Vaavu Atoll in the Maldives on May 14, Maldivian military diver Sgt. Mohamed Mahudhee also died while trying to retrieve their bodies.

The body of diving instructor Gianluca Benedetti was found at the mouth of the cave, along with four other divers – Monica Montefalcone, associate professor of ecology at the University of Genoa; daughter Giorgia Sommacal; Marine biologist Federico Gualtieri; and researcher Muriel Oddenino were found in the deepest part of the cave system.

But even though they are acutely aware of the dangers, there is something that constantly pulls back the cave divers who dedicate and sometimes sacrifice their lives to explore these strange underwater worlds.

Navigating only with flashlights and a guide (thin thread that allows divers to find their way back to the cave entrance), they see another side of life on Earth.

Cave divers often describe their chosen habitat as a completely different space-like world, filled with stalagmites, stalactites, and alien-like creatures. Heinerth, who has completed more than 8,000 dives, said diving in these underwater cave systems is “like swimming in the veins of Mother Earth.”

“Astronauts have the overview effect where they talk about looking back at the big blue planet, and they’ll never be able to look at Earth the same way again,” he told CNN on Tuesday. “I think I experience a similar effect from being on the planet… I am literally living on the planet, providing water to humanity, wildlife, and even all the industries we need for our modern life.”

‘Everything that could go wrong’

Many things can go wrong during a cave dive. Equipment may malfunction; rules can be broken; visibility can become almost impossible. And if things go wrong, you won’t be able to surface like in other types of scuba diving. You trust your own wisdom and your dive buddy.

While exploring these systems, cave divers will routinely pass through incredibly tight spaces. Heinerth said that sometimes “my shoulders are scraping the ceiling and my belly is on the floor and I can see the flow less than a meter high as the sand and silt hit my face.”

So before any dive, before doing anything else, Heinerth would “rehearse all the things that could go wrong, all the things that could kill me in this environment.”

“What if this hose suddenly breaks and I lose gas, can I reach this valve with the gear I’m wearing today?” he says.

“But it’s also a deep self-evaluation. Am I ready to take such a dive? And the last two questions I ask myself are: ‘Am I ready to rescue myself today with the equipment I have in the environment I’m in?’ and ‘Am I willing and able to save a friend in the same situation?’”

He also added that cave divers are normally incredibly well trained and prepared for any scenario.

“The last step I took is to leave the emotions on the surface… You have to stay with a pragmatic mind, ready to deal with any situation that may arise in reality,” he said.

It is not yet known why the five Italian divers never surfaced from their dive in the Maldives, but an investigation is ongoing to determine what happened and how they reached such depths.

Local officials said the group had permission to dive deeper than 30 meters (98 feet), where recreational diving in the Maldives is normally limited.

However, it is not yet clear whether they went deeper than planned or whether they were not properly equipped for such a technical and risky dive.

Vladimir Tochilov, a technical diving instructor who has researched this system before, told CNN that caves like this are rare in the Maldives. It is only 200 meters (656 feet) long and consists of several halls, but its depth “requires serious, serious training.”

underwater treasures

Underwater cave systems are treasure troves of information that provide an important source of data for biologists, physicists, paleontologists and historians.

“These caves are like natural history museums, providing information about Earth’s past climate, animals that lived their entire lives in darkness, as well as ancient civilizations that viewed these places as gateways to another world,” Heinerth said.

Some cave systems are home to endemic species, meaning these species are found nowhere else on the planet. By documenting such species, cave divers have aided our understanding of the planet’s evolutionary history.

Heinerth visited some caves that no other human had ever explored and will probably never explore again. As an underwater photographer, he said, “Bringing back jaw-dropping images from these places is very satisfying because it gives me a chance to share the adventure.”

But he is always wary of dangers. “My choices about risks will not only affect me, but they will also affect my family and my community,” he said. “So we need to learn from accidents and communicate honestly about what went wrong and how we can prevent them in the future.”

CNN’s Anna Chernova contributed to this report.

For more CNN news and newsletters, create an account at: CNN.com