How to achieve perfect buoyancy
Let's learn how we can become neutral buoyant. There are several factors affecting your buoyancy. Knowing and understanding how the equipment and movements we use and it's effects on buoyancy can be very helpful in achieving a state of good buoyancy. Sometimes we tend to forget how very little things can lead to a uncomfortable diving experience. Also you might frequently find yourself dropping like a rock to the top of reefs or banging against corals if you cannot properly control buoyancy.
Things that will change buoyancy
Before putting on your wet-suit, it's a good idea to soak it in water. It will make it easier to wear and reduce the air space between you and the suit. So when you jump into water it would take less time to fully fill your suit with water.
Make sure you don't have trapped air inside your suit, boots or gloves, because density of air varies depending on the depth. Neoprene wet diving suits can trap a lot of air bubbles between you and the suit. Wetting the inside of the diving suit before wearing them can help to remove a lot of them. The air bubbles will compress at deep depths and you become less buoyant, close to surface the bubbles will expand and you will become more buoyant. This is also one of the reasons, you will be more buoyant again at the end of the dive. There are other things too that can change your buoyancy throughout the dive such as the air tank.
Before descending it's a good idea to squeeze the BCD while hugging yourself as this will help in releasing the remaining air.
You must pay attention to any trapped air. Trapped air will compress under pressure and become more dense as you go deeper and when you descend it will become less dense.
Don't overweigh yourself
Many divers are over weighed. The reason might be, divers think you may not be able to descend if you don't use enough weights.
Carry enough weights just to be close to neutral buoyancy. You don't need a big chunk of weight to descend, a better way to descend and ascend is to use lungs often when necessary. And continue to breath normally when you feel like you want to level-off.
If you carry too much weights, you will have to rely on your BCD too much to become neutral buoyant. Since air in BCD changes density at various depths, you maybe fiddling with your BCD inflator constantly throughout the dive. And this will not be a pleasant thing for anyone.
Air has a considerate amount of weight, though it's hard to believe for many of us. At the start of the dive, the tank is heavier while it's full with air and as the dive progresses, the tank becomes more light as air is being used up by the diver. This is one of the reasons why you feel much buoyant at the end of the dive.
Frequently finding yourself out of air?
Some of the reasons why you are short of air.
1) Physical Fitness: - People with less aerobic fitness have higher Heart-beat rates and they gasp for air even for very less physical demanding activities. For such people a brisk walk of a few minutes might be overwhelming. People with better cardiovascular fitness have lower heart-beat rates and they consume less air.
2) Over weighing: - To balance diving weights, you have to use BCD to counter the force of weight. The buoyancy of weights remain constant throughout the dive. But the air-filled BCD will change it's buoyancy depending on the depth. The more deeper you go, the more it will be compressed reducing it's total volume. A football can easily float on the surface of the sea, but it might sink at very great depths. Carrying too much weights mean you have to put more air into BCD and keep it adjusted more frequently.
Enter water slightly deeper than your height. Hold a normal breath with an empty tank and BCD. You should be able to float in eye level while holding a normal breathe. When you exhale you should sink slowly, if not add more weights or reduce weights until you get the right amount of buoyancy. Make sure you're not too heavy or too light.
Get familiar with your equipment
A lot of diving accidents have occurred due to ignorance, because divers simply didn't knew about very basic things of their equipment. Injuries due to rapid ascent are common among divers.
Sometimes power inflator button on your BCD gets jammed and results in an uncontrolled ascent to the surface. You either have to disconnect the inflator hose or dump air from BCD. Sometimes divers are unable to locate the dump valves located on the BCD.
Control buoyancy using lungs
You can descend or ascend using lungs only. When you are neutral buoyant, you will oscillate up and down slightly while maintaining the same level.
Time and volume of air consumed during inhalation = Time and volume of air exhaled during exhalation
It is possible to change buoyancy by adjusting the time spend for inhalation or exhalation. As a general rule of thumb, if you spend more time for inhalation you will rise and more time for exhalation means sink. By adjusting the time, you can keep your lungs filled with air or with lesser air most of the time. You can control buoyancy by holding breathe too. But as a rule, in diving you never hold your breathe. This is to prevent lung-over expansion injuries. Whatever you do, always keep breathing.
To descend keep the inhalation time period as brief as possible. Inhale in a short burst and exhale slowly as you would normally do while emptying lungs. Since the amount of time spend during exhalation is more, you will sink.
To ascend keep the exhalation time period as brief as possible. Exhale in a short burst and inhale slowly as you would normally do while filling the lungs. Since the amount of time spend during inhalation is more, you will rise.
Trimming to stay leveled
Getting buoyant doesn't mean your upward force and weight are completely balanced. Actually you will never be exactly balanced. You will be either a bit heavy or light. It's just like driving a car, you constantly make yourself aligned with the road slowly as you continue driving straight.
If you are a bit heavy, try keeping your body at an angle with your head slightly above the level of your feet. This will keep you going forward and also give u a bit of lift keeping you leveled.
If you a bit light, try keeping your head a bit down, so you will be going forward and at the same time giving you a reverse lift which will keep you leveled. It's all about the angle you keep while kicking, adjust until you feel neutral.
People with higher body fat ratios have less density and can float easily. Generally women have higher body fat percentage than men and are more buoyant. Bodybuilders sink in swimming pools while average people can float easily.
Naturally the human body floats on water, but some people can float more easily. Even with all the diving equipment, our body will float. So that's why we need weights to counter buoyancy and to become neutral buoyant.
Difference between sea, lakes and swimming pools
Salt water is much heavier and denser than fresh water, so floating in salt water would be much more easier and our bodies tend to sink more in fresh water such as lakes and swimming pools.
Learning to control buoyancy takes time. There is only one way to master it, practice, practice and more practice. Experiment as much as possible whenever you go for a dive.