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Tuesday, 18 March 2014

Buoyancy Basics Part 4: Breath Control

Scuba Diving Basics

Breath Control for Buoyancy

As we continue to look at the basics of buoyancy control when Scuba Diving, we come to possibly the most common means of adjusting buoyancy, which is breathing.

As we discussed last week, the Buoyancy Control Device can be used to adjust a diver's buoyancy but the experienced diver will only use this for large changes in buoyancy such as ascent and descent. For minor changes, we prefer to use our lungs. Please bear in mind that this will only work for those using open circuit and rebreathers are a totally different kettle of fish!

Imagine you are scuba diving alongside a wall maintaining great buoyancy mid water at 30m when suddenly looming ahead of you is a beautiful Fan Coral in your direct line of travel. You decide that the easiest way to get around it is to ascend slightly and swim over it. What do you do?

One possibility is to add some air to the BCD to ascend but this will expand as you ascend and it gets a bit messy when you start adding and subtracting air from your BCD for these minor changes.

The best practice in this situation is to breathe in deeply. When we take a deep breath, we increase our buoyant force in the water (if you do not know what this is, please refer to our Buoyancy Basics 1 article) and become a little bit more positively buoyant. You will find that you begin to rise in the water, at which point, you simply have to begin to exhale for control.

Equally if you want to descend slightly, you can breathe out a bit further, making your lungs a bit emptier than you would normally have them. You will begin to descend and then you can just inhale for control.

At NO point should a Diver Hold their Breath!!!!

Using breath control to adjust your buoyancy is very easy but it does take a lot of practice to get it spot on. However, you will have already started to learn this technique with Hovering skills, ascent and descent training on your basic scuba diving courses.

I have seen a number of divers over the years that have insisted that all the dive should be controlled using breath control and only inexperienced divers have to use the BCD. 


There is a reason we have a BCD and it should be used to make big changes in buoyancy while breath control is for the small changes. If we didn't need the BCD, we wouldn't have it!

So when you are learning to improve your buoyancy skills when scuba diving, remember there are a number of things to consider underpinned by Archimedes Principle and Volume/Density relationships (which we will look into at a later date) and you have been given the tools to control buoyancy, so make use of them. You will find that the easier you can make your diving; with good weighting, using BCD and breath control, the easier it will be to achieve perfection.