Buoyancy Control

Along with ‘ear issues’ and ‘sucking air’, personal issues with ‘buoyancy control’ is an issue close to many diver’s hearts. For most people, particularly if they’ve had a good Instructor teach them in the first place, the relationship between your buoyancy control, you and your surroundings is something that is discussed and dissected during the PADI Open Water Course. You might not be that great at it - but you understand it…and understanding it is key to perfecting neutral buoyancy.

So without writing along essay on the subject I’ve drawn up a list of what to do, when to do it and why.

  1. Before going on your dive discuss your weighting requirements with your Instructor. If necessary do a weighting check in the pool, prior to going on your dive. Being over-weighted will effect your buoyancy control, as well as your air consumption - the two are linked.

  2. Add air to your BCD to float at the surface - this is called being positively buoyant.

  3. To sink, get yourself vertical - head up, feet down. Hold your inflator button HIGH above your head so that it too is vertical and remove all air. Stop finning and exhale. Exhaling reduces your lung volume making you more likely to sink.

  4. Once underwater start swimming. How do you feel? If you feel heavy or are using your arms a lot to stay where you want to be, then you are too heavy. Add some air into your BCD. Remember always one tap of air at a time, and allow for a pause between adding air. This is because inhaling = going up; exhaling = going down (although there is a time delay to make things a little less clear cut). If you are ‘negatively buoyant’ - too heavy then your legs will be dangling down - you won’t be streamlined and you’ll go through your air more quickly.

  5. If you are too light you’ll know because you’ll be heading up to the surface too quickly. You may also start exhaling to stay down and feel out of breath. Your legs will be higher than your torso and you’ll be fighting your body to get down. If you’re at the beginning of your dive and feel too light, then you’ll need to let your Instructor know so that they can donate you an extra weight. We’ll talk about if you are too light mid way through the dive in a moment.

  6. Let’s assume you feel just right - well then you are neutrally buoyant.

  7. Through out the dive your state of buoyancy will change. If you are weighted correctly in the first place then the following scenario should pan out:

    1. Once at your maximum depth chances are you’ll feel just a little too heavy. This is typically because you are at the start of your dive and your tank is full of air and heavy. Also as you’re at your maximum depth you’ll have the most pressure pushing down on you, also making you ‘heavy’. So its fairly normal to need to add a little bit of air into the BCD to compensate for this.

    2. As your dive progresses you’ll be using up the air in your tank. As you go through the air in your tank your tank will get lighter making you more buoyant. This is why you should start the dive being ‘slightly’ too heavy, to allow for this lightening of the tank.

    3. You’ll also start shallowing up, as you shallow up the air that you added into your BCD earlier on in your dive will start to expand. Think back to Chapter 1 in the PADI Open Water Manual and Volume/Depth/Pressure. Volume increases on the way up and decreases on the way down. So if you’ve say added one tap of air into your BCD down at 10 m, and you shallow up to 5 m. That 1 tap of air will turn into 1.5 taps of air. A seasoned diver is in tune with his/her body and will remove air before the extra air pushes him/her upwards. When you start out with diving it’s sometimes difficult to gauge when you’re shallowing up, so if you’ve not foreseen this happening you’ll need to correct your positioning in the water after it’s happened. So if you find yourself heading for the surface you’ll need to get yourself vertical, hold your inflator/deflator hose high above your head and remove air. Please note that the deflator button will not work effectively if you are in a horizontal position or the hose is kinked.

    4. Whilst you’re on your dive you may want to stop to look at something interesting. Try to practise making minor adjustments to your buoyancy naturally by adjusting your body positioning, swimming up or down or by breathing an extra big breath in or an extra long breath out. Don’t automatically reach out for the inflator or deflator button.

  8. Finally now let’s talk about buoyancy control and ascending. Whilst the maximum ascent rate by PADI is 18 metres or 60 feet per minute, most computers are set at 9 metres / 30 feet per minute - and that’s their maximum. So to go ultra slow is recommended. So in order to ascend slowly you’ll need to take all the air out of your BCD as you kick yourself upwards towards the surface. If diving with Tokoriki Diving, we’ll show you how to use your dive computer to assist you in ascending slowly. Word of advise. Even with all the air out your BCD please do not drop your inflator/deflator hose, as once you are at the surface you’ll need to have quick reactions to inflate your BCD all the way up so that you’ll be positively buoyant and floating at the surface.

There is a fantastic elective on the PADI Advanced Open Water Diver Course called ‘Peak Performance Buoyancy’. This involves a pool lesson followed by a dive, where you’re concentrating on understanding the principles of buoyancy. For sure practise makes perfect. So for those of you out there struggling with buoyancy and thinking that perhaps diving is just not for you…nonsense. Everyone can get great at buoyancy control it just takes a little bit of theory and lots of practise.