There are 3 concepts to learn and  2 questions to answer before using a neck weight in freediving.

3 Concepts to Learn:


During a proper freediving course, you will likely spend some classroom hours for theory and workshop practice, and a full explanation of the importance of equalization.  Equalization makes the pressure between the inside of your ears equal to the underwater environment to make your dive comfortable and avoid injury. To do so, we bring air, at regular intervals, from our lungs to our ears that we pressurize in general using Frenzel maneuver. Since freediving is diving deep in the water without using any external apparatus, freedivers only have the volume of one set of lungs worth of air to allow equalizing to happen. 

Residual Volume

As we dive deeper, underwater pressure increases and our lungs begin to compress (Boyle’s Law). There will come a point where our lungs reach their residual volume, which is the volume of air remaining in the lungs after maximum exhalation. For a regular person, the residual volume is 1/4th  to 1/5th  of the total lung capacity.  That means that when we reach 4 to 5 bars of pressure (30 to 40m), we reach our residual volume and we cannot bring any more air from our lungs to our upper airways in a natural way. We cannot equalize anymore.  

With training, we can reduce our residual volume. Some top athletes have a residual volume close to 1/10th of their total lung capacity. Still, at one point, they reach the depth of their residual volume where they cannot bring natural air from their lungs to equalize.


To overcome this limitation, the most used equalization technique used at depth is the mouthfill. The principle is very simple. Before reaching our residual volume, we bring enough air from our lungs to completely fill our mouth (cheeks fully inflated), and then we will use the air stored in the mouth to create the pressure necessary to equalize at depth.

The principle may be simple but the use of mouthfill is actually technical and needs constant refining for most Freedivers in order to achieve greater depths. If mouthfill can be tricky to use, it has to do with all the anatomical parts involved of which we have very little awareness. To perform the mouthfill in an efficient way, we need to have good control of our tongue (and not only the front part, of our soft pallet (the soft pallet can be trained and controlled precisely) and our glottis.

I will not go into more details about the technique of the mouthfill in this article, but to summarize, the tricky part is that if your glottis opens even a little, some air will be sucked back into your lungs. This can lead to the shrinking of the air that is in your mouth which makes creating pressure more difficult. Now, you need to rearrange the air in your mouth while making sure your glottis remains closed.

2 Questions to Answer:

freediving neck weight

Question 1: Will your neck weight interfere with your mouthfill?

It is now easy to picture why you want to avoid any physical distraction in the area where the front neck, chin, and throat are located. My past experience with artisanal neck weights is that they would always one way or another put some stress on one of these parts and disturb my mouthfill.  With the neck weights available in the market there are several lengths so you can choose the right one so that the end part comes and rest lightly on your jaw. 

Question 2 – What is the quality and material of the neck weight?

You can also shape it and reshape it as many times as you want or need to minimize the physical distraction to the mouthfill. The high-quality manufactured neck weight allows this without you needing to worry about breaking it. It is easy to adjust the shape perfectly so that you do not get any pressure on the throat or chin.

Finally, choose a neck weight with silicone material so that it sticks to the smooth skin of wetsuits. The neck weight should not move around at all during the dive. This is one less distraction. Since I favor smooth skin wetsuits, silicone material is the perfect fit for me.

Thibault Guignes

Based in Phillipines, Thibault is the owner of Camotes Freediving and holds the French record in Free Immersion (118m).

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