The story of the Blue Lake Project in Russia, diving in one of the largest and deepest karst springs in the world. Diving deeper than 200m this is the gripping story, soon to be a book, Martin tells the story behind the expedition to explore one of the largest and deepest Karst springs in the world, with all the challenges of deep CCR diving in very cold water and everything that can (and did) go wrong, including his DCS hit and the difficulties of the evacuation and subsequent treatment.