Cave Diving

The caves in the Bahamas were formed during the last ice age. With much of the Earth's water held in the form of glacial ice, the sea level fell hundreds of feet, leaving most of the Bahama banks, which are now covered in water, high and dry. Rain falling on the most porous limestone, slowly filtered down to sea level forming a lens where it contacted the denser salt water of the ocean permeating the spongy lime stone. The water at the interface, was acidic enough to dissolve away the limestone and form the caves. Then, as more ice formed and the sea level dropped even further, the caves became dry and rainwater dripping through the ceiling, over thousands of years, created the incredible crystal forests of stalagmites which now decorate the caves. Finally, when the ice melted and the sea level rose, the caves were reclaimed by the sea.
Central and Northern Florida, U.S.
The largest and most active cave diving community in the United States is in north-central Florida. The North Floridan Aquifer expels groundwater through numerous first-magnitude springs, each providing an entrance to the aquifer's labyrinthine cave system. These high-flow springs have resulted in Florida cave divers developing special techniques for exploring them, since some have such strong currents that it is impossible to swim against them.