Buoyancy Control
Buoyancy control is actually much deeper than most people understand. It requires an understanding that we are in a weightless environment. It is only weightless because we do things to make it so, such as adding or reducing weight or air. And understanding that something as small as an ounce of air can make a difference. An ounce of weight held out in any direction can make a difference.
One touch of the power inflator can change your buoyancy by as much as a pound and a half by adding as much as a pint and half of air. One pint of air equals of buoyancy. One kilo of air equals one kilo of buoyancy. Polishing the power inflator parts with a jewelers cloth. Polish the plastic removing any burrs, clean and polish the spring and push rod, and make sure there is no dirt in there. (Make sure a certified repair technician does this). Learn how to put just one bubble in the BCD to control your buoyancy, rather than just a full shot of air.
Understand that buoyancy control deals with breathing in a normal breathing range. It does not have to do with holding your breath or taking in full breaths, which can both decrease your safety and increase your buoyancy too much. Large movements of air cause dramatic changes of buoyancy on every inhalation and exhalation.
Try just taking a small dive light and hold it out in front of you and see what happens to your body. Hold it out to the side. See what happens. Your body will move in the direction of the physical weight. With a buddy, a really great exercise that I like having my students try in buoyancy control classes, have your buddy
Remove mask (make sure can breathe without a mask confidently)
Hover a foot off the bottom. Mask clearing and hovering have nothing to do with buoyancy control. Flood the mask. Then slowly remove the mask. Breathe without the mask. Replace the mask. Clear the mask. Do not rise or fall more than a couple of inches.
Buddy should be right there to make sure there is no more than a foot rise or fall. What you will find out is that simply flooding the mask will change your buoyancy. In moving your arms up you can change your position in the water and your buoyancy can change. In putting the mask on your buoyancy will change. As you go to put the mask on, the tendency is to hold one’s breath, so you rise.
Learn how important a single movement can be to your position in the water column. You will learn how to move slowly.
Slow down the normal volume of inhalation and exhalation – slow down a little bit.
When you take the mask off and on your breathing may change and just the physical motions can change your position in the water column. You may change the way you inhale and exhale. Eventually you will learn how to clear your mask as if you were making a normal exhalation. No force, no energy.
Now we begin to understand what the basics of true buoyancy control. Start looking at every piece of equipment on your body. How heavy are your normal legs, and then how heavy are they with your fins and booties, and perhaps exposure suit legs. If you are going to wear ankle weights for whatever reasons, don’t put on store bought 3 lb ones and expect to have perfect buoyancy. Go to the auto store and buy some old wheel weights and a little sac.
With rubber fins and weight suit- muscular legs may only need 4 oz. While the same legs in a drysuit with underwear may need half to three quarter pound of weight.
Make sure the weight is evenly placed on the weight – which does not necessarily mean symmetrical. See what happens by simply moving
Move the tank up and down in the back pack and see how your center of gravity is changed. You may find that you were wearing your tank in the back pack in the wrong place. Different tanks may require different location. Mark the tank with different colors of duct tape for each position in the tank band and then write in your log book how you felt with each tank position.
Assure that you never put the tank so low that you cannot perform an over the shoulder regulator retrieval. Don’t put weights in the pockets. Does your gear fit you at all. Does the BCD or weight suit fit. A drysuit that is too big even by a little will require more air in it to be comfortable, and hence requires more weight to be neutral. Now every tine you move, even the slightest amount of pressure change will cause air to expand or compress.
When there is too much air in the BC.. Air is affected directly by pressure. A two foot rise will cause the air to expand in direct proportion to its own volume. If I have one pint of air (16 oz) and I rise 2 feet, expansion will be in proportion to the pressure change, perhaps as much as an ounce. Now if I have ten pints of air, and I make the same two foot rise I have 160 oz of air, and obviously the reduction of pressure will be the same but the volume increase will be ten times large.
The shallower the water, the greater the volume change so the greater the buoyancy change. The same process is in direct proportion to lungs and how we breathe. Standard tidal volume is 1to 1 ½ pints of air.
Every movement we make, every breath is part of
Thank about what we are doing. And when we feel something didn’t work right, do it 3, 4, 5, ten times to make it better. Simply roll over in a spiral like a weight belt motion, feel what happens when you do it slower. Feel the air move in the BC. Control it, time it. Feel the air move in the drysuit, time it. Feel what happens when you push your arm against the BC to make the air move faster and change your position in the water column.
Feel what happens when you hold your gauges and move them to different parts of your body. Every breath and every movement you make will change your position in the water. Every minute of every dive is another opportunity to practice, hone, and memory path, another skill. Another movement and a different use of your breath, the air you carry in your BC and drysuit.
Buoyancy control is more than hovering in one place, it is more than a fin pivot., it is more than the ability to swim in a straight line and think you’ve got it. And it never requires breath holding, but rather, making very slight changes to speed and breath volume.
