World's longest flooded cave

"A group of divers has connected two underwater caverns in eastern Mexico to reveal what is believed to be the world's largest flooded cave, a discovery that could shed light on the ancient Maya civilisation. The Yucat'an peninsula is studded with monumental relics of the Maya people, whose cities drew on an extensive network of sinkholes known as cenotes. Some cenotes had religious significance to the Maya, whose descendants remain in the region "