This story appears in the August 2010 issue of National Geographic magazine. We sink into Stargate, sweeping the void with our dive lights. Fifty feet from the surface looms a pale haze, less ...

Beneath the land surface of the Bahamas, the underwater caves known as blue holes stretch for hundreds of miles in all directions. Today, these labyrinthine passages host a variety of tiny sea ...

A group of divers have connected two underwater caverns in eastern Mexico to reveal what is believed to be the biggest flooded cave on the planet, a discovery that could help shed new light on the ...

Sistema Sac Actun is the world’s largest underwater cave system. Stretching an astonishing 215 miles, this submerged labyrinth of tunnels, caverns, and crystal-clear waterways is not only a ...

Late at night on Jan. 18, 37-year-old Lorena Garcia Martin set out on a cave diving trip with her diving partner. The pair planned to explore the Cueva del Agua area, an underwater cave system in ...

But there is hope, says Thymann, and documenting this dense habitat of underwater caves may be the first step in protecting the manatees that live there. Receive a weekly dose of discovery in your ...