Beginner Tips: Buoyancy Control

If you inflate to ascend, you run a big risk of an out of control ascent.

Have you ever seen those divers out there just effortlessly floating inches above the bottom, moving as if they were one with the water, expending little, if any energy to swim around?  Ever wish you could do that too?  Well you can.  All it takes is some knowledge and practice.  And in my not so humble opinion, aside from an understanding of Boyle’s Law and how it relates to scuba diving, buoyancy control is the number one thing to have down pat.  I can help a wee bit with the knowledge, but the practice is all on you!

First off, why should you have good buoyancy control?  Well that’s a great question! It helps to understand why you should do something in the first place.  What advantages will good buoyancy control give you…

  • Less air consumption (you expend less energy, so you use less air)
  • Less effort – so you’re not as tired (and you use less air)
  • Lower chance of harming marine life (sorry about that crater hole in the reef!)
  • Lower chance of harming yourself ON marine life (like banging your face on fire coral)
  • Lower chance of harming yourself on ascent (oops, blew right through that safety stop!)
  • You don’t have to lug around as much weight (or pay as much in luggage fees)
  • You feel more at ease and comfortable in the water (as opposed to feeling like a large bull with an air supply)
  • You feel more in control
  • Because of the last two, you gain confidence
  • You look cool (this is, of course, the most important one)

Power inflator is NOT an elevator button

Okay, let me start off with one of my biggest concerns as an instructor.  Far too often, I give students the signal to go up and to my horror, they hit their power inflator.  Do. Not. Do. That.  I can’t stress this enough. It seems like I can tell students over and over again, yet their first inclination is to use the power inflator as an underwater elevator switch.   The only time a diver should be using their power inflator is to keep them from hitting/bumping along the bottom.  In other words, you don’t inflate to go up, you inflate to merely stop sinking; to stop or slow your descent.

If you inflate to ascend, you run a big risk of an out of control ascent.  Remember Boyle’s Law?  The air you put in at depth is going to expand as you go up, and the more you go up, the more buoyant you’re going to become. At a certain point, you’re not going to be able to control your ascent any longer and you will have put yourself at risk of DCS as you rocket to the surface like a cork. I’ve been there and done that, it’s not fun!

This may seem contrary to common sense, but you should only inflate to stop a descent and then you deflate while you’re ascending.  In other words, while underwater, you’re generally going to inflate on your way down (once you’re underwater and actually dropping) and deflate on your way up.  In fact, try to use your power inflator as little as possible in general, and when you do use it, make very small adjustments.

Okay, now that’s out of the way.

The Right Gear

First off, make sure your BCD fits properly. A BCD that’s too big or too small is going to make your buoyancy control that much more difficult. It should hug your body, not pinch it and not move around much independently. You want to make sure you have the right amount of lift for the diving conditions you’re going to be in, too. In colder water, you’ll need more weight due to thicker wetsuits, and your BCD needs to be able to handle that.

Weights and Trim
Once you’re clear on how to use your power inflator, or rather now NOT to use it, weights and trim are your next step in becoming a buoyancy control expert.  Lugging around too much weight underwater can increase your drag, force you to use much more air in your BCD to compensate, and will wear you out in the process.  Try this test. Go to a pool or some other easily accessible body of water. Do the buoyancy check (no air in BCD, holding breath, float at eye level) starting with zero extra weight. Then keep adding a couple pounds and redoing the check until you float at eye level with an empty BCD and a normal breath held.  Now, descend (remember to exhale fully!), and swim around to see how it feels.  Come back to the surface and grab 5 – 10 lbs of weight (the average amount of extra weight divers carry that they don’t need to) and descend again and swim around.  You will see how much more effort it takes to swim around with that extra weight.  Just try it. It may surprise you.  Remember that your descent should be slow. Another tip regarding weight checks: keep in mind that near the end of a dive your tank is going to be lighter, so you may need to put on a couple extra pounds in anticipation of that.

As much as you don’t want to be too heavy, you don’t want to be too light either. If you have to struggle to get down and you’re sure you’ve fully exhaled and fully emptied your BCD, then you’re underweighted. Don’t force yourself down because when you come back up on ascent with a lighter tank, you could end up with an out of control ascent.  Another tip about difficult descents:  Sometimes it’s just that the BCD isn’t completely empty.  Be sure to raise the inflator hose high, lean to the right a little, and lean back just a tad. That should get it completely empty.

Everyone is different when it comes to trim.  Do what makes you feel the most comfortable, but figuring that out may take some trial and error. Some folks are perfectly fine with all of their weight in their BCD front weight pockets.  Personally, I like my weight distributed all over my body. I wear ankle weights, tank weights, and put weight in my BCD front and back pockets.  That’s just me, though. Experiment with trim weights and see if it makes you feel more streamlined.

Look Ma, No Hands
While diving, your hands should be used to check gauges, computers, adjust your BCD, point at pretty things, and poke your buddy.  What they should not be used for is swimming.  Yes, sometimes you find yourself listing to one side or another. That’s where the trim weighting (see above) comes into play. Some of us have more muscle mass on one side or another and will just naturally tilt that way. Fix those problems with trim weights, not your hands.

Swimming with your hands in general is a big no-no in scuba diving. For one thing, it’s dangerous to all of the divers around you. Your flailing limbs are just unexpected obstacles they have to try to avoid so they don’t get smacked in the head, or their mask knocked off, or their regulator knocked out of their mouth. Secondly, you’re scaring all the fish away!  Third, you’re risking beating your limbs on someone or something and injuring yourself. Fourth (this list just keeps getting longer the more I think about it) you’re wasting energy and if you’re wasting energy, then you’re wasting air. That’s a scuba diving party foul. Fifth, it doesn’t help anything. Your legs are your power, your arms do very little underwater (see the whole wasted energy thing).  And last, you’re making it harder to feel the buoyancy adjustments you need to make.  By flailing around and using your hands to try to adjust your buoyancy, you’re not learning how to do it with your lungs or BCD.   You need to feel those sensations, understand them, and then compensate using your lungs, inflator, or your fins.

There are times that a rapid swimming adjustment must be made and hands must be used, but those are few and far between.  If you can’t seem to stop using them, then force yourself to clasp your hands together, or grab onto your BCD somewhere comfortable. Get your hands doing something else to help keep you from immediately flailing them out.

Body Position
Horizontal. That’s how you should be diving. Not only diving, but it’s how you should descend too.  As you descend, you start to pick up speed as your wetsuit compresses and the atmospheres add up above you. If you make yourself horizontal as you’re descending you can more easily see the bottom you are plummeting towards, and as your body creates more drag it will naturally slow your descent. Small bursts of air will help control your body too, and help to prevent you from cratering into the sediment or reef below. If you’re not sure what cratering is, go to the bottom of a lake, quarry, etc, where a lot of new divers are being trained and just watch. You’ll see them drop like rocks to the bottom then hit the bottom with a great big POOF! as a crater is formed in the sediment around where they landed. That’s cratering. Stop doing that.

Horizontal is best while swimming around too. Not slightly angled up… not slightly angled down. Either of those positions means you’re not weighted properly. You should be horizontal for ease of movement, range of vision, and best buoyancy control.  If you’re angled slightly up, each fin kick is going to move you up, vice versa for being angled down. Just like driving, people tend to go the direction they are looking. Be aware of this and try to maintain a horizontal position, and if you do look up to take in some scenery, stop kicking.


Just Breathe
Remember a couple paragraphs up I said that you should use your power inflator as little as possible?   You may have wondered how, or why.  The answer to both is: use your lungs.  Once you’ve used your inflator to get neutrally buoyant on your initial descent, you really should rely primarily on your lungs from there on out. Big deep breaths will cause you to rise a little in the water column, big deep exhales will make you drop a bit. Use these to your advantage while diving and you’ll find that you’ll need to kick less and spend less time fighting your buoyancy because you accidentally added too much air to your BCD.  The only way to truly master this is to practice, practice, practice.  You know that brief hovering skill you did for your open water cert? You should be practicing that all the time until it becomes natural for you. It’s real easy to just grab that inflator and pop some air in, but fight that urge. Try using your lungs instead.  Imagine this scenario:

You’re diving along a beautiful reef when you come to an area you need to go up and over.  You take a deeper than normal breath and let your natural buoyancy lift you gently upward as you continue with your normal kicking. Once you’re up a little bit, you resume breathing normally.  Then, as you need to come down the other side, you exhale deeper than usual, allowing yourself to easily sink deeper in the water before resuming your normal breathing cadence. 

Doesn’t that sound much better than kicking your way up and kicking your way back down? Or putting air in your BCD, only to realize that once you do go up a little bit that you’re too buoyant and must now let air back out as you fight to get back down to your desired depth?

I was a pack a day smoker for nearly 20 years and I quit a couple years ago. My doctor says that my lungs are in better condition than many non-smokers, and that she would never have guessed I smoked at all, much less that I smoked so much for so long. I’d like to think that exercising my lungs this way while scuba diving helped a lot with that. So, not only will it help you with your buoyancy, but it could help your health too! Just breathe.

One of the biggest problems with newer divers is that they’re very tense, with good reason.  You know how you did a weight check in a pool somewhere and you know what weight you should be using, but you just can’t seem to go down right now?  Chances are you’re all tensed up and are holding extra air in your lungs. You don’t even realize you’re doing it, it’s just a matter of not being relaxed and the air just isn’t coming out.  I know it’s easier said than done sometimes, but relax.  Take some nice deep cleansing breaths, and let them fully out. I tell people to fully exhale and they blow out a little puff.  Most of us don’t realize just how much air our lungs can and do hold. Practice relaxing your muscles to allow yourself to really fully exhale.  Do it on land when you are very relaxed so you can feel what it’s like to fully exhale, then remember that when you’re trying to descend.

Aside from descending issue, being tensed up in general will affect your buoyancy control. Have you ever tried to float on your back on the surface of the water while tensed up?  You can’t do it. You have to relax to float.  Well, at least I do!  Similarly, you need to relax to have good buoyancy control underwater too. This takes some time, comfort, and confidence to get there though.  Speaking of which…

Practice Makes Perfect
You have to practice these things. The best divers among us weren’t born knowing how to float effortlessly while sitting in a buddha fin-holding position. It takes practice to get there.  We can tell you what you need to do, we can give you pointers, we can show you, and we can tell you what works and what won’t, but to master this you need to feel it.  And that, my friends, is a very personal thing that you have to attain on your own. Eventually, it will click. That lightbulb will go on and you’ll wonder why it seemed so hard to begin with. I promise you. Practice will make perfect. Every chance you get, just do it. You’ll thank me later when you’re carrying less weight, using less air, feeling less tired, and aren’t being maimed from crashing into reefs.