Documentary exploring the deep caves of the Yucatán Peninsula, Mexico, and the ancient relics of the Mayans. Cameras follow a team of specialist divers as they make their way through the ancient cenotes and navigate a complex underwater network of caves, often having to squeeze through tiny holes and crevices. Along their journey the team discover ancient relics of the Maya people who believed the pits were an entrance to the underworld, known as Xibalba meaning place of fear, and used them as a place to make sacrificial offerings to their gods.