Secrets of the Maya Underworld. Beneath the jungle-clad temples of Mexico's Yucatan, lies the world's largest network of flooded caves and subterranean rivers. Divers exploring this surreal landscape have discovered strange new animals, as well as remains of the ancient Mayans. Simon MacCorkindale narrates. Producer Tim Scoones ; Series editor Tim Martin
Repeated next Sunday (AD) www.bbc.co.uk/nature