Macalady doesn't dive, but she's an active dry ... Dean’s Blue Hole—Earth’s deepest known underwater cave—plunges more than 600 feet into darkness. The entry to South Passage is decorated ...

The floor and walls open up and divers are surrounded by darkness — but herein lies ... Commission requires divers to have proper cave-diving certifications and they must follow a registration ...

“They swim in them or use them for drinking water.” Diving into a pitch-black cave isn’t as scary as it might sound, said Calderon Gutierrez, who is accompanied by local guides and divers.