Don't Sweat What You Can't Fix

Several years ago, we put six divers side by side on a measured course. All swam exactly the same speed at the same depth using the same fins. Their other equipment was not identical but very similar. All six were very experienced, relaxed divers. We expected to see nearly the same air consumption for all six.

To our surprise, however, their air consumption ranged from 38.3 to 85 psi--while swimming the same distance at the same speed and depth. Even excluding the best and worst, the differences were amazing. The middle four divers ranged from 41.2 to 60.3 psi.

What accounts for these huge differences? The air hog was by far the heaviest, so he had to push aside the greatest amount of water with every foot of travel. A small woman had the lowest air consumption, nearly tied by a tall, thin, torpedo-shaped male. But even divers who were fairly similar in size had very different air consumption figures that couldn't be explained by differences in fatigue, stress or skill.

Why? They were, like all of us, different people with different lungs, different cardiovascular systems, different metabolisms, different genes. The lesson here is that there is no ideal air consumption rate and that you shouldn't be ashamed for using more air than your buddy. You can only do what you can.

So let's have less comparing of gauges and less chest thumping over which of us can make a tank last longest. Conserving air is a means to an end. A large cushion of extra air is useful only if it translates into a longer, safer or more enjoyable dive. But if all you're after is bragging rights to having the most air left over at the end of a dive, maybe you're missing the point of diving in the first place.

Having the most air at the end of the dive is not the proof of diving excellence that we sometimes make it. Unless your name is Willy.

 

Several easy fixes will reduce your air consumption, and though none of them is as important as slowing down and breathing efficiently, they do add up.

 

• Check your gear. An obvious one is to check your equipment for air leaks--or ask your buddy to check. Often, you can't see the leaks yourself. A little bubbling from your tank O-ring or your BC inflator can add up to several hundred psi over an hour's dive. An octo that free-flows occasionally will dump air a lot faster. Detune it if you can, and mount it with the mouthpiece facing down. Don't detune your primary reg, however. You'll increase the work you have to do to suck in air, which will increase your carbon dioxide production, which will accelerate your breathing rate and, in the end, waste air.
   
• Streamline and simplify. Minimize the "hole in the water" made by your body. The less water you have to shove aside, the less energy and air you have to consume. One way is to reduce how much lead you carry because extra lead needs extra BC inflation to support it. An inflated BC pushes aside more water. Another way to shove less water is trim your body to horizontal, so your legs are following through the hole made by your shoulders and not enlarging it. Many divers do, in fact, swim with their heads up and fins down.
   
• Watch your kick cycle. Finning with short, rapid strokes also causes less turbulence and drag. When you spread your legs wide for a big stroke, your fins are actually slowing you down. Rapid finning takes getting used to, however. It may be tiring and even waste energy and air until your legs are trained to it.
   
• Go slow, stay shallow. Depth and current both waste energy and air. Doubling your depth doubles your air consumption, and if you double your speed to compensate for a current you may nearly quadruple your air consumption. So dodge both when you can. Often, a wall looks the same at 40 feet as it does at 60. On the other hand, there are trade-offs: a current may be weaker along the bottom than near the surface.
   
• Stretch your boundaries. Consider taking up yoga for more control of your breathing. Don't laugh. Free divers swear by it.