NAUI Scuba Diver 100 Diving Science sit, or stand on coral reefs or other marine life can damage or kill these creatures. Diving without buoyancy control is tiring, hazardous, and a sign of an unskilled, unthinking, and uncaring diver. Buoyancy Checks Different people have different amounts of personal buoyancy. Some people float higher, some float lower, and some people actually sink, even with their lungs full of air (figure 4-12). You must check to determine your buoyancy in the water. To check your personal buoyancy, use the following steps, wearing a bathing suit in fresh water: 1. Assume a vertical position in the water. You must remain motionless. 2. Inhale a deep breath of air and hold it. If you can hang motionless at any level, totally submerged, you are neutral. If any part of your head is out of the water, you are buoyant. If you sink, you are not. 3. Exhale the air in your lungs. Your chest deflates and you displace less water so you will start to sink, unless you are very buoyant. 4. Kick back to the surface. You can also try this experiment in salt water to see the difference. Your instructor will recommend how much lead weight you should put on a weight belt based on your personal buoyancy and gear. The lead weights divers wear to adjust buoyancy are many times more dense than water. By selecting the right amount of weight, you can adjust your buoyancy to be neutral at depth. Before you begin a dive, you must check to see how buoyant you are with your gear on. To check your buoyancy for diving, use the following steps: 1. Assume a vertical position in the water. You must remain motionless. 2. Inhale a normal breath of air and hold it. 3. Vent or dump all of the air from your BC. If you float at eye level, you are properly weighted. If your head is higher out of the water, you are too buoyant. If your head is in the water, you are too heavy. 4. Exhale the air in your lungs. Your chest deflates and you displace less water so you will start to sink. 5. Kick back to the surface and inflate your BC. 6. Change the weight on your weight belt, if FIGURE 4-11. IT IS ACCEPTABLE TO KNEEL IN SAND, BUT IT IS NOT ACCEPTABLE TO KNEEL ON CORAL, OR OTHER UNDERWATER CREATURES. FIGURE 4-12. THE AVERAGE PERSON CAN FLOAT MOTIONLESS AT THE SURFACE WITH THEIR LUNGS FULL OF AIR.
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