Blog about Underwater Life and Scuba Diving

Buoyancy – Get Neutral, Horizontal and Efficient!

1 Star2 Stars3 Stars4 Stars5 Stars (2 votes, average: 5.00 out of 5)
Loading...Loading...

The Need For Buoyancy Control

Even the most novice diver knows that buoyancy in diving is important, despite it being one of the most difficult skills to master in the sport. A diver’s ability to maintain good buoyancy will drastically affect every other aspect of their diving; from their air usage to their ability to assist other divers.

Good buoyancy is the mark of an experienced diver, yet it is often only taught to a basic standard in the open water level of tuition, the rest is left to the diver to pick up as they go. This guide offers some simple troubleshooting for those of you who feel that your understanding of buoyancy is basic at best, or it might just serve as a stimulus to spend the next two dives really focusing on getting your position in the water just right.

Technique

It is almost impossible to “teach” technique via the written word but it is possible to give some hard learn advice. The primary factor in buoyancy control is your breathing. Ultimately there is little to explain about buoyancy – air will make you float and lead will make you sink, apply or expel enough of each to achieve desired result…done. But it’s not quite that easy, is it? Because we must breathe by in-taking a lung full of air and expelling it we constantly alter our buoyancy. This doesn’t mean that we, as humans, cannot achieve fish-like stability when diving, it simply means that we must use our lungs to help us control our attitude in the water.

There are many ways in which a diver can breathe to change his depth and position, but it is always best to adopt a deep, slow breathing rhythm that will reduce dead-air consumption from the regulator and allow you to carefully modulate your buoyancy by breathing in/out a little slower or faster. This does not mean that you have been given permission to hold your breath by me, this is still a number one no-no, but a slightly slower exhale will leave air in your lungs for longer and will give you slightly more positive buoyancy. Simple things like this change you from a rookie diver into a competent one.

Equipment

We are land animals, meaning that we are not designed to spend any extended time underwater. Sure, we can hold our breath and swim down but that does not equate to hovering motionless or gliding freely when submerged. This is because almost all humans are either positive or negatively buoyant and require aid to stay still in water. The gear that enables comfortable diving is quite extensive and can be a little tricky to master at first.  Now we will look at the gear that helps, and the gear that affects, our buoyancy.

Weight Systems

The obvious and primary equipment for countering your body and suit’s positive force is ballast, usually in the form of lead weights. It’s the great curse of every dive professional to have to guess the weights for their divers. Knowing how much weight a diver needs is difficult and relies on many factors including the diver’s experience, the type of dive, the gear they are using and their body size. The best bet is to do a buoyancy check at the surface with a near-empty tank.

Another thing to consider is not just how much lead you take with you, but how you intend to distribute it on your body. There are many weight systems that each have their own advantages and disadvantages:

  • Block – A simple system of different sized blocks of lead with space to thread a nylon belt through – good for quick weight belt assembly but can be uncomfortable and difficult to arrange for perfect trim. Tip: ensure the blocks are symmetrical on your belt and body, try moving the blocks towards your hips for better balance. Also, if you pass the belt through one eye of the block, twist it and feed it through the other then the block will not slip on the belt.

     

  • Shot – This is very small lead balls that are poured into pockets on a belt. This allows for perfect weight distribution and more comfort, but is fiddly, time consuming and only good for personal weight belts. (i.e. Not rental)

    Shot Weight Belt System

  • Integrated – This system is more and more common now and provides a very comfortable way to carry your lead as it is built into the BCD itself. It tends to put the weight on your hips and is easy to jettison. Tip: most integrated weight BCDs have trim pockets at the back of the jacket – use these to alter your position in the water for better horizontal diving or easier vertical sitting.

Tanks

Tanks affect your buoyancy greatly being as they are bulky and heavy. A good tank choice for your dive can greatly reduce the amount of lead required for your weight system. Though other types of tank exist, the following are the two you are most likely to encounter:

  • Aluminum – Generally used in tropical countries where metal corrosion is a worry and where less buoyant exposure suits are generally used. They are negatively buoyant but not by much. They tend to be larger than steel tanks to carry the same amount of air.
  • Steel – These tanks are more dense and can carry air at higher pressures. This makes for a heavier tank. If you are diving in a dry suit then a large steel tank vastly reduces the amount of lead you will need and if you are in a long wetsuit then you might be able to loose the weight belt altogether.

    Steel Tanks Come In Many Sizes

Exposure Suit

Exposure suits keep you warm by putting a barrier of air or gas between you and the water. The colder the water, the more gas you need, the more buoyant the suit. A 3mm shortie is only 1kg-2kg buoyant, but a 7mm long suit with vest and hood might be more like 5kg-7kg. This depends on the size of the person of course.

 

Tip: when any gas is taken underwater it compresses which means it is less buoyant – this applies to exposure suits which means that their buoyancy at 10m is different to that at 40m – remember to add air to your BCD or dry suit as you descend to compensate, and discharge it as you ascend.

There are many kinds of suit but here they are broadly split into two for convenience:

  • Wetsuit – A wetsuit is comprised of tiny, isolated gas bubbles trapped in neoprene. This gaseous neoprene floats very easily and is very easy to predict – the more neoprene needed, the more lead needed to keep it down. This is important when buying a wetsuit – only buy the style you need – if 5mm will do then don’t take a 7mm, your buoyancy and flexibility will suffer otherwise.
  • Drysuit – This is a sealed suit that traps either air or gas inside it and stops the water from coming into contact with the diver at all. This is much more buoyant and requires a different approach to weighting as your whole body becomes positive. Some divers require ankle weights to maintain horizontal trim. Unless using a really heavy tank system you will require quite a large amount of weight which means positioning is critical. Ensure the buckle is in good order on your belt and that you have the belt on tight – if it slides on your body you will be diving on your side which is not a good look!

BCD (Buoyancy Control Device)

I bet you were wondering when I’d get round to writing about this crucial piece of buoyancy gear being as the clue is in the name – buoyancy control device! The BCD is essentially a jacket that can be filled or depleted of air from a hose via a button. This allows you to offset the weight of your gear and remain neutral at any depth or float comfortably on the surface.

A well fitting BCD with a good wing will allow a diver to coast in the water perfectly horizontal – it acts just as a plane wing does and offers stability while swimming.

A BCD With Wing Will Help A Diver Glide

Tip: Many rookie divers think that it doesn’t matter how heavy you make your weight belt as you can always compensate for it with your BCD. Although this is true, a full BCD is uncomfortable, causes excess drag (affects air consumption) and the air tends to move around in the jacket which tips you off balance. Try to get your weight down to an optimum level for better diving.

Fins and Auxiliary Gear

It is important to note that all of your gear has an effect on your buoyancy, either positive or negative. A torch and reel in one pocket might cause you to dive lopsided so it’s important to ensure even distribution of your gear. It might also affect your weight for the dive too – perhaps a heavy torch will mean you can loose a kilo off your weight belt on your night dive.

Another big factor in a diver’s buoyancy is their fins. A pair of modern, high-end fins will likely be positively buoyant which might affect you if you are wearing a dry suit. Likewise, a pair of heavy old Jetfins and a shorty might cause you to hang leg-heavy in your dive. Pay attention to these things and you will quickly attain a perfect, horizontal water position.

Old Style Fins Can Alter Your Position In The Water – Pay Attention To This

Final Tips

There are some things that affect your buoyancy that are a bit more difficult to alter, namely your body and it’s composition. It is basically true that a smaller, denser person (more muscle/less fat) will require less weight and a larger, less dense person will need more. There are big variables at work in this statement and it is definitely not true for all people, but generally this is the case.

One last point to mention is that by relaxing, and by this I mean actively trying to calm down and enjoy yourself, you will find that you pick up and maintain a smooth and reliable breathing rhythm, you will hold your breath less and you will be more able to feel your body in the water – this is a big key to gaining control of your buoyancy – awareness of yourself while diving.

By Jamie Campbell


Tagged as: , ,

Comments

  • Noreen said:

    Hi!! Maybe you can help me with a questions I’ve had for years (and I’m an experienced diver and AI). Given: an object is buoyed up by the weight of the water it displaces. I’m assuming that as a submerged diver, I displace the same amount of water whether I’m in a prone position or curled into a ball. Maybe this is a mistake. If this it true, then why, when I’m perfectly neutral in a prone position do I sink if I curl into a ball? Any light you can shed will be greatly appreciated.

    Thanks.

  • Jamie Campbell said:

    @Noreen

    Hey Noreen,

    That’s a really interesting problem that I’m not familiar with in practice. However, after a little thought over a big mug of coffee I wonder if it’s possible that by curling your body up into a ball you are compressing your lungs which forces you to exhale slightly, thus making you less bouyant? What do you think?

    Good question!

    Jamie

  • Lionel Wong said:

    Hi Noreen,
    Here’s my 2 cents’ worth.

    Ever wonder why a crumpled ball of paper drops down faster than a sheet of clean paper when dropped from the same distance?

    My guess is your surface area and the upward resistance you face in the water. When you are in prone position your surface area in contact with the water is greater, hence greater resistance by the water. When you are curled up there is less surface area in contact with the water and hence less resistance.

    Hope it helps!

    Lionel Wong, Singapore

  • GULLIVER (Author) said:

    Thanks for comment

  • Carlos Sousa said:

    Hello,
    i´m a begginer at this matters of diving, but i do have a problem, and maybe you can help me.
    after the descend, its almost impossible to me, to stay in the horizontal position. i´m always vertical, and if i inale air ,then i just simple start to go up.
    at the diving center, they give me 4kgs of weight, to put in the belt, i´m 1.73cm height and 74kg weight.
    Can you help me?

    thanks

    Best regards

    Carlos

Trackbacks

There are no trackbacks



Blog Roll