Breathing underwater has some analogies to breathing above water ... first and foremost, the harder you work, the more air your body requires. It's simple physiology ... work makes your body produce carbon dioxide, and the buildup of CO2 in your bloodstream is what triggers your brain to take the next breath.
So, knowing that, the best way to reduce your air consumption while diving is to reduce the production of CO2. This generally means reducing the effort you put into what you're doing. As an analogy, consider the difference in how hard you breathe when you're sitting on the sofa, compared to when you're out doing yard work.
So how do we do that?
Well, let's start by working on buoyancy control. The objective is to be able to manage your buoyancy with your lungs ... the BCD should be used minimally, and only to compensate for the expansion/compression of air spaces in your exposure suit as you change depth. Weighting factors heavily into that consideration, which is why it's important to be properly weighted. So doing a weight check is a good first step. I do mine at around 8 feet, since (remember) after your safety stop is over you will still have to control your buoyancy for a slow ascent to the surface.
So how do you know if you're overweighted? Well, stop kicking and see what happens. If you have to add air to your BCD to keep from sinking, then you're probably overweighted. You shouldn't need to kick to stay off the bottom.
Another factor is developing good trim ... in other words, you want to present as little of your body as possible to the water in the direction of travel. Water is extremely heavy stuff, and it takes a lot of effort to move it out of your way. If you're in a horizontal position, you're moving minimal water with each fin kick. If you're diagonal to the direction of travel, you need to push a lot more water out of your way, and that takes a lot more effort ... then we're back to that CO2 buildup problem again.
So how to achieve a horizontal trim? Well, by moving your weights around till you achieve a neutral "axis of rotation" when you stop kicking. In other words ... when you're properly trimmed, then stopping all motion (no hands or feet movement) should result in your being able to hold still in whatever position you were in when you stopped. Any head-down rotation means your weights are too high on your body, and you should consider moving some of them lower. Conversely, feet-down rotation means your weights are too low, and something needs to get placed higher on your body. Keep in mind that you can do some of this by sliding your tank up or down ... but there are limits to how much you can achieve that way.
Weighting also affects trim ... one of the surest signs of being overweighted is the necessity to constantly kick from a diagonal orientation in order to maintain your position in the water column ... if that's you, then try removing some weight.
Slow down ... most new divers are jetting around like baby harbor seals trying to see everything. Well, believe it or not, you're probably missing an awful lot of stuff because you're swimming past it so fast it doesn't even register. Lots of critters blend in with their surroundings, and if you go too fast you won't even see them. Slow down and enjoy the scenery ... that's why we're down there.
Don't swim with your hands. In scuba diving, the motor's in the back (your fins). Your hands are very ineffective, and will cause you to work much, MUCH harder to go where you want to go. Learn to keep your upper body "quiet" by clasping your hands together and putting them in close to your chest as you dive.
And finally, learn to breathe properly ... slowly and deeply. An inhale should take 3 or 4 seconds, followed by a slight pause (about a second to allow your lungs a good O2 to CO2 exchange), followed by an exhale of at least 4 to 6 seconds. In other words, you should be taking no more than about 6 to 8 breaths a minute and they should be full-deep breaths.
Summary ...
- proper weighting
- proper trim
- slow swimming speed
- good breathing technique
These will get your started. Once you've achieved a reasonable comfort level with these techniques, you can "fine tune" by working on developing a gliding "frog" kick, which will get your where you're going (under most conditions) with much less effort than the flutter kick we all start out with.
... Bob (Grateful Diver)
