National Geographic : 2010 Aug
"All of a sudden, it's got you," says photographer Wes Skiles of the "insanely dangerous" vortex in Chimney Blue Hole (left) off Grand Bahama. Like a giant bathtub drain, it sucks down millions of gallons when the tide comes in. "It's like going over a waterfall---there's no escape." Keeping his distance, a diver sets up equipment to measure the whirlpool's flow rate. From a protected cove on Long Island, Dean's Blue Hole (above)---Earth's deepest known underwater cave---plunges more than 600 feet into darkness.