This workbook captures the best current practices in overhead instruction into one convenient workbook that will last a student from initial cavern training up through the full cave certification and that provides a great resource for reviewing important material by the seasoned cave diver. The workbook has been specially crafted to match the current NACD Standards & Procedures. This will enhance the quality of the experience for the student and provide a common standard for training at all levels. The workbook is upwards of 150 pages and includes useful outlines, photos and illustrations, cave maps, discussions and extensive calculations for gas math.