Tuesday, Feb. 9 at 8 p.m.
Nova – Extreme Cave Diving

Blue holes are underwater caves that formed during the last ice age when sea level was nearly 400 feet below what it is today. They are Earth’s least explored and perhaps most dangerous frontiers. With an interdisciplinary team of climatologists, paleontologists and anthropologists, Dr. KennyBroad investigates the hidden history of Earth’s climate as revealed by finds in this spectacularly beautiful “alternate universe.”