Marcus Thomas is a full-time graphic designer, as well as a writer and photographer, based in Wellington. He has spent a lifetime exploring New Zealand's underworld and been at the forefront of exploring the longest cave system, Bulmer Cavern. Neil Silverwood hails from the West Coast and is a professional photographer specialising in places many would consider too difficult or dangerous to go for a photo. Assignments have been as varied as capturing New Zealand's wildest canyons to skiing in war-torn Afghanistan. Silverwood regularly shoots for a range of magazines both within New Zealand and around the world, including regular contributions to New Zealand Geographic. Thomas and Silverwood have just published a book, Caves: Exploring New Zealand's Subterranean Wilderness, which takes readers on a journey into New Zealand's longest and deepest caves, through one of the world's most dangerous cave dives, and prospecting for a totally new kind of cave on a South Island glacier.