Eric waved to his diving partner, pointing in the direction of the underwater cave. His partner, Lazaro Bravo, was twenty meters downstream, carried by a current that Eric would use to glide in slowly behind.

In the distance Lazaro’s light flickered out. Eric touched the button on his transducer, his voice crackling into an electric wave. “Lazaro? Where’s your light?”

“¡Dios mío!” he answered. “Won’t believe it, muchacho. Won’t need light here. Is amazing!”

The current accelerated. At first it was dark – a dull mixture of rocks and sand, but then the siphon pulled him down deep into a light brighter than the mid-day sun.

He got his bearings and looked around for Lazaro who waved in slow motion. “¡Aqui esta!”

Eric put his hand over his eyes, shielding them from the light below. Above him the cave’s mouth was twisted into an evil grin. To each side were boundless silver sands cascading against luminous fields of crystalline stalagmites.

“Amazing!” Lazaro said.

“Yes,” Eric said, “but how do we get out?”