Each year, an average of 20 people drown while cave diving. For this survival scenario, survival experts Cody and Dave are lost divers who are fortunate to find air, but they are deep inside a maze of caves in Belize. Equipped with only their dive gear — mask, fins, wetsuit, buoyancy compensator and flashlights — they must find their way out and to safety. The survival rules that work above ground, like following a river downstream, don't apply in the labyrinth of underground caves. Instead, they must make their way upstream in a trek that puts Cody's barefoot philosophy to the ultimate test. Once they emerge, the situation goes from bad to worse — they find themselves surrounded by dense jungle, a web of vines and thorn ravaged terrain... and snakes.