When the pandemic shut down his travels, he shifted his attention to caves in his own backyard. Instead of rappelling a few hundred feet down vertical shafts in splintering ice, he swims deep inside underwater caverns in the porous limestone of the giant Floridan aquifer to document their failing health.

Springs are formed when outcrops of the limestone aquifer, which lies beneath the ground, rise above the surface and groundwater emerges, creating cool, clear pools and rivers brimming with aquatic plants and animals. The springs have been in trouble for decades, fouled by pollutants from agricultural runoff and sewage leakage and overdrawn to provide drinking water to 90 percent of Florida’s 22 million residents.

Gulley, who is also