It was a great show. Hadn't seen it before, but it's a must-see when you get a chance. Serious treatment of cave divers and their equipment, plus great underwater footage of the systems. Excellent scientific work on paleotonlogy, archaeology, geology, and climatology. The lengthwise cross section of the stalagmite showing the major climate change events, and tracking of the iron back to the Sahara was fascinating. Dedicated in memory of Wes Skiles. Glad we watched.