Two decades later, I organized a series of expeditions to investigate new deep caves, using dye traces in ... before a new team from our Call of the Abyss project set out to surpass the record ...

The Hranice Abyss — or "Hranická propast," in Czech — is the deepest known freshwater cave in the world. Geologists think it could extend more than half a mile (1 kilometer) below Earth's ...

Outside the cave, it’s a blistering 100°F ... the other angles upward and traverses an abyss—a deep pit or possibly a lake, I can’t tell—and disappears into a hole 20 feet above me.