When Czech tourist Dan Frolec embarked on a Croatian holiday with friends over two decades ago, he anticipated a blissful week of Adriatic sun, sailing, and scuba diving adventures. The group of eight experienced divers planned leisurely afternoons on boats, deep-sea explorations, and coastal dining in one of Europe's most picturesque regions. Instead, their 2002 excursion descended into a harrowing tragedy that claimed two lives and saw Dan detained for five weeks under suspicion of murder.
The Fateful Dive That Changed Everything
Now 55 and residing in Bali with his family, Dan has chronicled the traumatic events in his new book, The Cave, released online this week. The publication details how a routine underwater exploration spiralled into an international investigation, intense media scrutiny, and a prolonged legal battle that threatened his freedom.
The group had been enjoying several days along Croatia's stunning coastline when they anchored in Poganica bay, remembered by Dan as a "beautiful bay" where they relished afternoon sunshine and seaside meals. While examining nautical charts, they noticed a mysterious circled marking on the seabed. The boat's owner suggested it might be a hole, though its exact nature remained unknown. Intrigued, the divers agreed to investigate the following afternoon.
A Deceptive Underwater Discovery
Four divers initially descended, exploring near the vessel before returning to announce they had discovered an underwater cave. Dan's friend, Miroslav, who had been snorkelling near the surface, decided to join the subsequent exploration. Dan recalls Miroslav saying, "I don't want to die… I will go snorkelling just with you to see what it is." The area appeared safe—approximately 10 metres deep and close to the boat.
Unbeknownst to the group, Miroslav missed the others by mere minutes. Dive computer data later revealed he reached the cave entrance just four minutes after they had exited. Believing his companions were still inside, he entered alone.
The cave proved dangerously deceptive. From the seabed, it appeared as a two-metre-wide dark opening, but actually dropped like a chimney from 10 to about 22 metres, branching into complex caverns and corridors. When the four divers resurfaced and discussed their find, Dan asked about Miroslav's whereabouts. They hadn't seen him.
The Desperate Search and Tragic Consequences
Approximately forty minutes after Miroslav entered the water, the group realised he must have ventured in alone. With his air supply dwindling, time became critical. Despite extensive searching, they couldn't locate him. Dan explains how underwater caves often contain fine silt that clings to surfaces. "When you exhale bubbles... the sand starts kind of falling... visibility drops to zero," he describes. He believes Miroslav became disoriented, unable to distinguish between the cave interior and open water.
After an hour of futile searching, the Croatian Navy was summoned. Their divers, however, lacked cave-diving training, delaying proper searches until the next morning. During the rescue operation, one Navy diver became lost but resurfaced, while another perished below the surface.
Accusation and Interrogation
Still unaware of Miroslav's fate, Dan and his friends were taken for questioning at a local police station. The interrogation quickly intensified, with Dan becoming the primary focus. He underwent polygraph testing and was repeatedly asked if he had murdered his friend. During questioning, police disclosed for the first time that Miroslav had been found with a knife in his chest.
"They attached me to the polygraph… 'Do you know how Miroslav died?'… 'Do you know it was a murder… that he had knife in the chest?'" Dan recalls. He believes this tactic aimed to exhaust and confuse him into confessing.
Weeks of Detention and Speculation
The investigation dragged on for weeks. Beyond the station walls, scuba diving forums buzzed with speculation. However, data from dive computers and smart watches indicated Miroslav had reached the cave floor long before Navy divers entered, ruling out foul play or external involvement.
Regarding his friend's probable fate, Dan suggests Miroslav may have taken his own life upon realising his air was running out. "There are many people who get lost in the caves and then basically drown," he notes. In extreme conditions, panic and oxygen deprivation can lead to such desperate decisions.
Dive computer data showed Miroslav swimming near the cave ceiling at around 22 metres, likely seeking an exit. Suddenly, it recorded a rapid descent to 54 metres—the cave's bottom. Dan interprets this as the moment Miroslav lost consciousness or died.
Inconclusive Evidence and Eventual Release
The autopsy proved inconclusive, showing signs of both drowning and a fatal knife wound. Dan asserts authorities fixated on the knife while largely ignoring drowning evidence. After five weeks, due to insufficient evidence, Dan and his friends were released. An investigating judge dismissed police claims, concluding the death was most likely an accident followed by suicide.
Dan speculates the case was driven by a need to assign blame, potentially diverting attention from internal failures during the Navy rescue that resulted in the death of a senior officer's son.
Media Portrayal and Lasting Impact
The incident dominated headlines in Croatia and the Czech Republic, with Dan portrayed very differently across borders. His home country showed support, while Croatian media maintained an accusatory stance.
Beyond the legal ordeal, Dan speaks most painfully about loss. He describes taking a photograph of Miroslav on the boat shortly before the dive, where his friend ate his last meal and enjoyed the sunshine. The image was later printed on canvas, framed, and given to Miroslav's mother. "Our life was damaged and impacted… but not like for her," Dan reflects.
Processing Trauma Through Writing
It took Dan about a year to adjust after his release. Though the experience never left him, it gradually stopped feeling actively "threatening" and "scary." Writing The Cave became a means to process events and reclaim narrative control.
Looking back, Dan still replays the moment Miroslav decided to dive alone. "He is going underwater alone… which is against the rules. Many times I thought to tell him: 'Hey, but you're going on your own? Are you sure?'" he says. "He was quite tough, and he was kind of also experienced... so, maybe he would have gone anyway."
Leadership in Crisis and Safety Advice
Dan takes pride in how the group responded upon realising Miroslav was missing. His management experience enabled him to lead calmly in the crisis. "I was leading a multi-national, you know, team in my job. In that moment, I said, 'Hey guys, hold on. No panic. We need to now make a plan and try to find him and do everything the best we can,'" he explains.
For fellow travellers and adventurers planning similar trips abroad, Dan emphasises thorough preparation and respecting unfamiliar environments. "Get local intelligence, in terms of somebody who's been there - who has been to the mountain, who has been in the cave. Talk to them, then follow their advice. Ask yourself: Am I equipped for that? Do I have enough training?" he advises. "Because those kind of things are super important. Don't just go and find out."
