(This program is no longer available for streaming.) Follow a fearless team of scientists as they venture into blue holes—underwater caves that formed during the last ice age, when sea level was ...

Cave diving combines the thrill of scuba diving and with the excitement of exploring a cave; it’s a challenging activity even for experienced explorers. At these four sites — some of the most popular ...

On Sunday’s episode of The Excerpt podcast: Hidden beneath Earth’s surface are caverns and pathways that hold the secrets of our planet’s very beginnings. Even after decades of exploration, there are ...