Inside the Bahamas' Blue Holes

USA Today leads us into an upcoming National Geographic feature on the wonders and weird science provided inside the Bahamas' blue holes.

What lies below the Bahamas in the Caribbean? A veiled world of fossils, blind creatures and scientific riddles.

In next month's issue of National Geographic magazine, an international team of cave divers led by anthropologist Kenny Broad of the University of Miami reveals the mysteries hidden from vacationers' view.

The two-month expedition, paid for by the National Geographic Society, was merely a small slice of time in a years-long effort to uncover the secrets of this realm, which has been plumbed by researchers for at least three decades.

Only a few miles inland from the Bahamas' sparkling coral reefs, the islands' limestone boasts dozens of submerged caves, "blue holes," some of them hidden in what look like island swimming holes linked to the ocean.

But swimming holes they are not. The inland caves on five islands sport freshwater caps covering heavier saltwater layers, sometimes filled with clouds of poisonous hydrogen sulfide released by salt-eating microbes, acting to preserve whatever falls within. Others contain whirlpools powered by the tides.

"Cave diving is really about knowing your limits," Broad says. "But it provides one of the most amazing experiences in life, and the scientific opportunities are tremendous."

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