NOVA (1974) : 37x13

"Extreme Cave Diving" follows a fearless team of scientists as they venture into blue holes—underwater caves that formed during the last ice age, when sea level was nearly 400 feet below what it is today. These caves, little-known treasures of the Bahamas, are one of Earth's least explored and perhaps most dangerous frontiers. The interdisciplinary team of biologists, climatologists, and anthropologists, led by renowned cave explorer Kenny Broad, discover intriguing evidence of the earliest human inhabitants of the islands, find animals seen nowhere else on Earth, and recover a remarkable record of the planet's climate. The stakes are high as the scientists swim hundreds of feet through narrow, dark passages that have trapped and killed divers in the past, but the scientific payoff is considerable.