How To Improve Your Buoyancy February 21, 2020 by lukesheppard

Good Buoyancy is one of those skills that you can’t really learn from a book. You can probably do quite well, assembling kit and regulator recovery type skills from some decent book reading but buoyancy control is just one of those things that you learn by doing. Neutral buoyancy is a balancing act between the negative, sinky stuff, like your lead weight and torch and anything that will sink basically, all added up, and the positive, floaty stuff, like you and your wetsuit, and your BCD, or Buoyancy Control Device, makes up the difference. 

Buoyancy is all to do with the weight of the water that you displace. If you imagine the amount of space that you and your dive gear takes up and fill that up with water. If all of that water weighs the same as you and your gear then you’re gonna be neutrally buoyant. If you inhale or inflate your BCD, then you take up more space but your weight hasn’t changed so now displacing more water and the water that you’ve displaced weighs more than you do so you float.

Back in the day, old school divers didn’t have BCDs so they had to sort their weights out perfectly to be neutrally buoyant but the invention of the BCD makes your life a lot easier. It also allows for all of your gear that changes buoyancy during the dive, but I’ll take about that later. There is plenty of advice on how to improve your buoyancy and most of it works to be honest but probably the best advice is to just go diving more. The more time you spend in the water the more your body will learn what’s going on in the water.

Sign up to a local club or dive trip so that you can get in the water more often than once a year. By being in the water more often then you’ll relax more and this, in turn, will help your buoyancy because you’ve done it a hundred times, the only thing that changes is the scenery. Shallow water is where the most extreme buoyancy changes occur so if you can practice there then that’s the best place really.

So let’s take a look at how to improve your buoyancy.

End Some Dives Right

The best way to improve your buoyancy is at the end of a dive to do a proper buoyancy check. Most divers are taught to do a buoyancy check at the beginning of a dive so they float at a certain level with an empty BCD but the best time to do a buoyancy check is at the end of a dive with a near-empty tank. At the end of a dive, or if you have access to a tank with 50bar or 500psi or so in it, you want to dump all of the gas out of your BCD and drysuit and see if you can hover just under the surface, if you can, perfect.

If you find yourself sinking then you’re wearing too much lead, so it’s obviously best to do this in shallow water, I probably should have lead with that. But take off small amounts of lead until you stop sinking. Full tanks are less buoyant and you shouldn’t be ending dives with less than 30bar so if you can stay under with the amount of lead you have left on your belt then that’s all you should need. Right at the end of a dive is going to be when you’re at your most positive buoyancy, unless you’ve been picking stuff up. So if you can stay down just under the surface with what little lead you have left is the most lead you should really need on a dive.

With less lead on your belt, you won’t need to adjust your buoyancy as much during a dive which is the true point of this exercise. You won’t have an excess volume of gas on your back, compensating for the extra lead you’re carrying, that gas changes volume and buoyancy as you ascend and descend so cut away any excess weight because it’s actually ruining your buoyancy and air consumption. At most you only want to be using a tiny amount of gas to adjust your buoyancy at depth if any. Just take a look at your dive guide or Instructor and how little they touch their inflator during a dive.

Trim yourself

Once you’ve got the correct amount of lead on your weight belt, you need to put it in the right place. This is where a buddy comes in handy. Book some time out with your buddy in the water where you’re both kitted up and try to hover in the horizontal position. Now don’t move or correct your position, just let your body turn whichever way it does, sometimes closing your eyes helps, but make sure you’re in a safe environment and your buddy can stop you turning turtle or anything. Your buddy will be able to see what’s going on and then together you can move some of your lead where it needs to go, usually back on the surface where it’s safe to do so.

All of your lead on a weight belt is convenient, but that may put you in a head-up position. If so then take some off your belt and put it closer to your shoulders, either in trim pockets, on your cam band, or if you can on your shoulder straps themselves and this will bring your shoulders down so you’re flat in the water. Others tend to have floaty legs and that’s why we have ankle weights. The amount of lead on you doesn’t change but where it is in relation to your centre of buoyancy does. If you don’t need that much -ve weight on your feet then maybe consider a heavier pair of fins, some manufacturers are actually measuring their fins buoyancy so you can better decide if they’re for you or not.

Once you and your buddy have spent a while sorting out your trim, your buoyancy will improve because you can relax on a dive not having to constantly fight to stay in the right position. Swimming diagonally with your feet down increases your drag because your swimming against more water and you also always swimming a little bit upwards, so you swim in this zig-zag pattern constantly adjusting depth and buoyancy.

Wing up

There’s a reason why tech divers and more advanced divers dive wing style BCDs and other than the customisability, it’s the buoyancy characteristics. Wings have all of the positive buoyancy on your back around your tank and they hold you in a great horizontal position when they have gas in them. One of the biggest complaints about wing style BCDs from divers is that they put you in a face-down position on the surface when fully inflated, which is what they’re designed to do so it’s not a design flaw, just deflate your wing a bit and you’ll float upright. If you need a fully inflated wing to stay on the surface then go back to the first point, you’re wearing too much lead.

Wings also don’t tend to trap air because they’re just a round donut shape. Jacket style BCDs have pesky pockets and sections that can trap air when you’re in a certain position. You don’t want trapped air anywhere on you and when you’re ascending you want to be able to get rid of it quickly if you need to. Wings allow for this because all of the air is all basically on the same level so you can purge it easily. At worst you may need to dip your right shoulder or look up a bit so the air migrates to your left shoulder but a jacket may need a squeeze and a jiggle and a shuffle to get the gas to the right spot.

Wings also tend to be pretty minimalist so you don’t have all this excess material of unknown buoyancy all over it. You get the material of the bladder itself, the straps, the backplate if you’re using one and any bits and bobs you choose. The more stuff you load onto yourself for a dive the more it will affect your buoyancy so take it easy and if you don’t need it, don’t bring it. If you dive with special stuff like a camera rig then try to weight it properly instead of yourself. Don’t be trying to hold this buoyant thing down with your weight belt or drag this heavy thing around, try to make anything like that as neutral as possible so you don’t need to worry about it pulling you around. Unless it’s a DVP, that’s what it’s supposed to do, just make it neutrally buoyant.

Changing Buoyancy

This is the tricky bit, as you learnt in your introductory course as you swim down the pressure increases and gas volume reduces in a given air space. The balloon gets smaller as you swim down deeper. If you’re wearing a wetsuit or a drysuit then those air spaces shrink down as the pressure increases. The amount of water they displace changes too which changes your buoyancy. Also, consider how good your wetsuit seals are, it can take a good few minutes for all of the air trapped inside your wetsuit lining to bubble out, it may not be much but it could be enough to skew your buoyancy check at the beginning of a dive.

Buoyancy is all to do with the weight of the water that you displace and that’s why we get runaway ascents and also runaway descents. As you ascend the trapped air in your wetsuit and BCD expand so they displace more water so they become more buoyant so you float more so they expand more and so on until you reach the surface. If you have tonnes of air in your BCD at depth it’s going to increase in size more than if you only have a tiny amount of air in your BCD. Putting numbers to it if you’re at 10m or 33ft with 1oz of air in your BCD and ascend to the surface then you’ll end up with 2oz.  If you start with 2oz you’ll end up with 4oz so you want as little excess air space on you during your dive as possible. If we could find a better alternative to wet and drysuits we’d switch but air and argon is just too darn insulating.

Your tank is another that most divers don’t realise changes buoyancy during a dive. Steel tanks sink when empty and full but there is a slight difference. The difference is more obvious in some ali tanks because they can go from negative buoyancy when full to positive buoyancy when empty and that’s because the weight of the compressed gas inside is changing, not by much but enough to change the buoyancy during the dive, that’s why we do that buoyancy check at the beginning of this video with an empty tank.

Log It All

Most of my logbook pages cover the gear I’m wearing, where I am, how much lead I have and how my buoyancy was on that dive. I remember my dives and the amazing things I’ve seen but the main reason I look back at old dives it to check how much lead I should put on my belt. If you’ve put all of this work into correcting your weighting then you might as well log it correctly and include everything. All of the kit that you’re wearing, where you are, what type of tank you’re using what type of suit because it’s all going to affect your buoyancy and if you’ve dived something similar then that’s a good starting point.

When I dive somewhere new I look at the kit that I’m going to be using and look up a similar dive and work out my weighting from there. That way I know for example that on sidemount I tend to be light on my shoulders so I move lead up over my shoulders. I’ll only need a couple kilos of lead in saltwater in a rash vest, without logging this it’s easy to forget and it just saves a lot of faffing around on dive one, you can just go diving.

So there were a few of my tips on better buoyancy, but the trick is to relax and just dive more. Use your lungs before your BCD and most people dive too much lead. If you inflate your BCD longer than that to get neutrally buoyant at depth, then you’ve probably got too much lead. But what tips do you have? Let us know in the comments below and stay tuned on the channel for some more advice videos to help make you a better diver. Thanks for watching and safe diving.