Frank McGill, who has extensive diving experience, has been scuba diving near Essaara in The Republic of Guinea on the coast of the South Pacific for several months, along with some cave explorations. However, these trivial expeditions cannot satisfy McGill's ambitions, because there is a huge cave that has not yet been discovered. This cave, respected as the "Mother of Caves", is the largest, deepest, most complex, dangerous, and most majestic and beautiful cave in the world. In order to become a famous explorer in history and to create a world record for human cave diving, McGairla invested and recruited a group of elite soldiers to prepare for cave exploration.
Everything at the beginning went very smoothly. All the team members showed good professional quality, all the equipment was top-notch, and all the plans looked seamless. However, with the deepening of the expedition team, nature began to show off gradually-the road became narrower, the water flow became more and more turbulent, and the underwater terrain became more and more complicated.
At this time, The Republic of Guinea included the rainy season, and a severe tropical storm hit the country. The continuous heavy rain caused the river to rise, and the underground water level also rose. The rain poured into the depths of the cave, forming a "flood" underground. The huge flood became an obstacle to the expedition team. After losing a few members, McGill, Josh in the team and their patron Carl Horley had to change their original path in the face of shortages of food and drinking water. Back to the escape plan at the entrance of the cave. They can only find the way to the ocean in the complex cave water body by diving
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