Divers explore the world's longest underwater cave in Mexico spanning 325 miles

The Ox Bel Ha, Mayan for 'Three Paths of Water', is a sprawling water 'web' that makes up the world's longest underwater cave system. In this vast network, researchers have found giant sink holes, huge crystal chambers known as ice palaces, and 38 unique species of cave-dwelling animals. Cave divers have mapped out 325.6 miles (524 kilometres) of subterranean tunnels, but believe there could be even more yet to explore.