Expedition

(ominous music) (letters click) This is the Yucatan Peninsula. It is about 200 miles across, separating the Gulf of Mexico and the Caribbean. It's almost completely flat, and doesn't appear to be extraordinarily interesting. But unbelievably, this area here could well be the most ripe place on the planet for exploration. All of that, though, happens below the ground. Beneath the jungle floor lies a honeycomb of subterranean cabins which are filled with water, known as Cenotes. I'm diving with cave dive expert, Bernadette Carrion. What an incredible place. Wow. The cavern's just so vast. (Carrion) This just just remarkably beautiful It's such a fragile environment. (soft music) Are those (mumbles). It's beautiful. And it's all done by the dripping of water Unbelievable, eh? It's not what you expect to see with fish swimming around it. But these stunning wonders of nature, are under threat. Right on their door step is the fastest growing tourist hot spot in the world. People come here in millions to stay in luxury hotels that are sighted right on top of the underground cave system. And I get my first taste of the effects of this mass tourism as we make our way into the jungle. Turns out, that the best way for us to get into the forrest is through the town dump. It's kind of a vision of hell but you know, everywhere has to get rid of rubbish some how. But here, outside of Talu in the Yukatan. Because of what we know about the geology here it's kind of got much more impact. Loads of pollutions are going down into the cave systems and the fresh water that is flowing through them is the same fresh water that the people here and the animals completely rely on. It's a shocking discovery. Unwarily beneath this rubbish dump, lies a fragile world. Yeah. It's absolutely beautiful. I think in the 21st century, we all have a tendency to think that all the great explorers were generations ago but that's not true. There still are still places like this that are spectacular, magnificent. It completely blows my mind to think that below so much of the Yukatan like this. As yet, never seen by human beings. These caves extend for hundreds or kilometers and in land its estimated only one percent have been explored. This could be the greatest place for exploration for my kids, for my grandkids and their kids. There is more potential here than I can even get my head around. It's horrifying to think that such pristine water could be under threat for increased tourism. You see these wonderful caves. The water that runs through it, that everybody here relys on. And at the same time you see the rubbish in the development above that's just dripping straight down into that precious water. This is somewhere that if we're not careful could be destroyed before it's even close to being explored. We must do everything we can to make sure that these extraordinary cenotes are here for the next generation.