We travel to the Blue Holes of the Bahamas and explore the mysterious point at which freshwater meets saltwater. On the Cook Islands in the South Pacific, Nan Hauser studies the communication behaviour of humpback wales. Why do whales produce these sounds? We accompany glaciologists on a unique and dangerous expedition to Spitsbergen. The scientists want to gain access to the interior of a glacier and find out why these white giants are slipping faster and faster into the sea.