NAUI Master Scuba Diver 232 Diving Techniques and Deeper Diving intend to pass your primary second stage to your buddy in case of an out-of-air emergency, switch the longer hose to your primary second stage and use the shorter hose on your octopus rig. You will also find this shorter hose length makes it easier to manage the octopus rig while it is not in use. Divers do not usually have immediate access to professional medical care. Carry a first aid kit and preferably oxygen, and be prepared to render first aid. Pre-dive planning includes inspection of equipment before the dive and checking its operation before entering the water. Uncomfortable incidents have been precipitated by as simple an oversight as a missing snorkel purge valve or a badly deteriorated fin strap. Before entering the water, verify operation of your primary and secondary second stages, buoyancy compensator inflator valve, submersible pressure gauge, reserve valve (if present), and compass. BUOYANCY CONTROL Buoyancy control is the mark of a skilled diver. The ability to hover, float up, or sink at will is essential to enjoyable diving (figure 10-3). Under most diving conditions, a diver endeavors to be neutrally buoyant throughout the dive. A number of factors affect your buoyancy, and some are personal, while others depend on your equipment. To achieve buoyancy control skill, you must learn to control these factors. The percentage of muscle, bone, and fat in your body are personal factors that affect your personal buoyancy. Individuals with a large percentage of muscle and/ or with large, dense bones, are often not buoyant, and those with a greater percentage of fat are often buoyant. Be aware of changes during periods of weight gain or weight loss. The amount of air in your lungs greatly affects your buoyancy. With practice, you will become skilled in controlling your vertical movement by changing this volume of air. By making long exhalations, you can retain less air, thereby slowing your ascent rate or assisting in your initial descent. Conversely, taking deeper breaths will slow a too-rapid descent by making you closer FIGURE 10-3. NEUTRAL BUOYANCY to buoyant. The difference between a full lung and an empty one can change your buoyancy by as much as eight pounds, depending on your lung capacity. Other factors controlling your buoyancy relate to your equipment and objects you carry. Several items of equipment make you buoyant, such as your exposure suit, some buoyancy compensators (because of air trapped in the foam padding and between the inner bag and the cover), and some cylinders (usually aluminum, but also some steel) when empty or nearly so. The amount of buoyancy from an exposure suit changes with depth because of the compression of the air or neoprene. Divers must individually determine the
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