In the heart of Thailand's Satun province, an exciting expedition took place - the Satun Cave Exploration Project. This ambitious project was dedicated to studying the practically unknown system of underwater caves and its connections to numerous sinkholes located in the Pharayabangsa mountain massif. The area lies within the Satun National Park, and diving was possible only thanks to special permission.

While the main mission goal was to delve into the intricacies of the complex aquatic ecosystem of these caves, the team also planned to search for traces of the lost Phap Phaeo tribe, which inhabited these lands for centuries but disappeared mysteriously several decades ago. Although local residents found traces of their burials, it is still unknown what exactly happened to this once fairly numerous tribe. Unfortunately, no clues or traces were found in the caves that could be useful in solving the mystery.

One of the most important discoveries during the expedition was made in Toh Wang Cave. According to local legends, adventurers explored it during the dry season, reaching up to 600 meters into the cave. The team members believed that the flooded part of the cave extended much further. Indeed, a series of dives conducted during the expedition proved that the underwater passages of Toh Wang extend much further, leading several kilometers from its entrance to nearby sinkholes.

The dives were carried out in sidemount configuration, both with an open circuit and using KISS Sidewinder CCR rebreathers. The compact size of this rebreather enabled exploration despite encountering many very tight restrictions.

The team set a record by installing nearly a kilometer of guide line, confirming Toh Wang as the longest freshwater cave in Thailand. During the expedition, other underwater caves were also discovered in the vicinity, suggesting the existence of a complex network of connections within this 20-kilometer mountain range.

The expedition to this hidden world aimed to uncover secrets that had been hidden for centuries, shedding light on the fascinating history and biological diversity of this remote region of Thailand.