There’s an alien world beneath our feet. What could it teach us about life?

Deep in the dense jungle of Mexico, pools of water that dot the thick vegetation may resemble the shallow ponds found in forests all over the world. But these seemingly boring puddles are actually deep sinkholes, or cenotes as they are known locally, and form portals to another world.

Thomas Iliffe and David Brankovits aren’t hesitant to enter these watery portals. Clad in wet suits and headlamps, and lugging multiple oxygen tanks and sample jars, the two biologists and their colleagues have plunged into the murky cenote waters many times.

As they dive down, sometimes as deep as 80 feet below the surface, the water becomes so crystal clear it almost seems as if they could remove their respirators and take a breath – despite being sometimes as far as 1,000 feet from breathable air.

At times they have to wriggle through