More air means more dive time and more dive time means more fun. That alone is reason enough to practice these tips for getting the most out of every tank. But there are other reasons as well: a bigger safety reserve for emergencies and the priceless feeling of never having to cut a dive short because your tank is running low.
Repair leaking O-rings and fittings anywhere on your regulator and BC. Don't forget gauge console swivels since a small stream of bubbles from a high pressure leak and is actually more air than you would imagine.
Overhaul your regulator regularly because when it is operating at peak efficiency, you waste less energy trying to suck air through it.
Make sure your octopus doesn't free flow. You may elect to have your licensed regulator technician "de-tune" it a bit. And, be sure to secure it so that the mouthpiece is facing downward.
Streamline yourself and your gear. More drag moving through the water means more energy expended. Leave behind anything you are not going to use on the dive. Of the rest, put what you can in BC pockets instead of letting it dangle on D-rings. If it has to dangle, clip it close to your body. Stow your snorkel in a pocket or strap it to your leg with your knife.
We are taught to "breathe normally" under water but that advice is more aimed at getting you to relax and simplify the lesson at conserving air. In fact, the most efficient underwater breathing pattern is not "normal" at all.
Breathe deeply. A deeper breath brings air to more of the tiny "air sacs" (alveoli) in your lungs where gas exchange actually takes place. It also adds more fresh air to the volume of "dead air" that remains in your lungs, throat, and mouth from the previous breath, so the mix is richer. Although each breath uses more air, you will take fewer breaths and the net effect will be less air used.
TIP: Concentrate on a complete exhalation. This reduces the amount of "dead air" you re-breathe and keeps your level of carbon dioxide (CO2) lower. Higher CO2 will trigger the next breath even though your blood oxygen level is still adequate. On the other hand, a deep exhalation extends the time before you feel the need for another breath.
Breathe more slowly. As air passes from tank to lungs, turbulence is created at each narrow opening and corner turned. Turbulence restricts air flow. The work of breathing is obvious in the breathing resistance you feel from even the best of regulators. Some turbulence is unavoidable, but the amount of it goes up dramatically when you try to breathe quickly - just as a faster-moving boat creates a bigger wake. To minimize resistance, move the air slowly - suck the air in slowly, push the air out slowly.
TIP: Breathe slower at depth. Turbulence increases with depth because the air is denser. Concentrating on a slow breathing rate will pay even bigger dividends on deeper dives. Pause after inhaling. Give those alveoli more time to work by holding that breath for a few seconds before exhaling. To avoid any risk of embolism, hold your breath by holding your lung expansion with your diaphragm. Do not close you epiglottis but keep your chest expanded and your airway open. On the surface, your normal breathing pattern is inhale-exhale-pause. Under water, a more efficient pattern is inhale-pause-exhale-pause-inhale-pause-exhale-pause . . .
TIP: Try yoga. Seriously! Yoga exercises teach awareness and control of your breathing pattern. Divers who practice yoga generally report their air consumption rate goes down.
Relax: Easier said than done. But when you are relaxed, you naturally breathe more slowly and deeply. On the other hand, rapid shallow breathing is your body's natural response to anxiety. Anxiety occurs when physical and emotional stresses accumulate. In order to relax, you need to stop, identify what's causing stress and deal with it.
Improve your aerobic conditioning. Better aerobic conditioning means you can do more work at a lower breathing rate. "Out of breath" is almost synonymous for "out of shape". And it's likely, though not proven, that a stronger cardiovascular system is more efficient at off-gassing nitrogen too.
Move slowly. This goes with breathing slowly. Water creates turbulence - friction - as it passes over your body. Turbulence goes up exponentially with speed, which means swimming twice as fast produces something like four times as much turbulence, which requires four times as much energy to overcome. Producing that energy uses four times as much air. All your movements, not just your swimming, should be slow and deliberate. Turn around slowly, reach to tighten your fin straps slowly. Do everything as if you were submerged in molasses.
Fin efficiently. Again, the goal is to minimize turbulence. Generally speaking, fairly short fin strokes, where the fins stay within the slipstream of your body, produce the most thrust with the least drag. Likewise, kick mostly from the hips, not the knees. "Propellor or split" fins generally call for a shorter, faster stroke than the more traditional paddle fins.
Don't use your hands. Minimize the frontal area you push through the water by keeping your hands to your sides. An easy way to do this is to clasp your hands together. Try to achieve a posture as nearly horizontal as possible so your fins follow through the "hole" made in the water by your body. Don't drag your tail (fins lower than your body).
TIP: While paddling with your hands wastes energy, pulling yourself across the bottom from rock to rock or along a rope saves energy. Likewise, when trying to maintain your position in surge or current, it saves energy to hold-on to a rock. Obviously, this is not acceptable with live coral as we are not to touch live coral.
Minimize your weight. Carrying extra weight required extra BC inflation to achieve neutral buoyancy. The air used to inflate the BC is probably insignificant but the extra drag caused by the larger, inflated BC is not. For the least effort in swimming, try to carry no more than the weight necessary to make you neutral at 15 feet with a nearly empty (buoyant) tank.
TIP: Take a class. Minimum weighting depends on precise buoyancy control. And that comes only with practice. But classes in weighting and buoyancy control are available and can greatly shorten your learning curve.
Stay warm. Wear enough exposure protection to stay warm. When you are chilled, your body burns energy (and uses air to do it) to generate heat. In a clam shell, fighting being cold wastes air.
TIP: Even 82? water is cool enough to chill you on repeated dives without exposure protection. You may not feel cold, but your body does lose heat and does use energy to replace it.
TIP: Wear a hood. Wearing a hood of any thickness allows you to use a thinner wetsuit because your head is a comparatively large source of heat loss.
Airing An Opinion (PUN)
Don't you just hate that dreaded question: "How much air ya' got left?" When another diver brags about having 200 psi more air than you at the end of the dive, chances are he's really trying to say that he's a better diver, more relaxed and in tune with the sea or something. He may be that - or he may simply be smaller - or have a different metabolism - or have followed a slightly shallower dive profile. Or he may be a she: most women use less air than most men. But because numbers are so easily compared, the amount of air you have left has become a convenient shorthand for how good a diver you are.
Convenient, but not very accurate. In fact, divers are not created equal and there is no ideal air consumption rate to which all divers should aspire. Sure, if you use 1,000 pounds more than your buddy in the same amount of time, you've got a problem which you should - and can - correct. But, a 200-300-pound difference is meaningless.