Deep within the complex web of Florida's aquifers, a diver releases dye in the crystal clear waters of Ginnie Springs to determine the path of the current. Unlike deep sea diving, where depth and uncontrolled ascent are the great dangers, the peril of cave diving is disorientation. The currents swirling between tunnels and caves don't always lead back to open water.

(Text adapted from and photograph shot on assignment for, but not published in, "Unlocking the Labyrinth of North Florida Springs," March 1999, National Geographic magazine)