Cenotes are natural swimming holes formed by the collapse of porous limestone bedrock, which has revealed a secret...

Cenotes are natural swimming holes formed by the collapse of porous limestone bedrock, which has revealed a secret subterranean world of groundwater pools. Most cave cenotes have fresh water that has been meticulously filtered by the earth, making them so clear and pure that you can see straight through to small fish frolicking in the plant life below. Open-air cenotes also have clear water, and often are home to vitamin- and mineral-rich algae that nourish and protect your skin

Know more:
http://www.divecenotesmexico.com/cenotes
http://www.lonelyplanet.com/mexico/yucatan-peninsula/travel-tips-and-articles/secret-swims-the-cenotes-of-mexicos-yucatan-peninsula#ixzz3XkV8zgF4

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