How Deep To Charge The Mouthfill

sfsdiving
Jun 21
3 min read

Different Types of Mouthfill Charges

One of the biggest misconceptions with mouthfill is that there is one "correct" charging depth. In reality, the depth you charge depends entirely on the purpose of the dive.

Sometimes we're performing a depth dive and charging as deep as comfortably possible. Other times, we're deliberately charging shallow to practise the skill safely and gather data.

Simulation and Drill Dives

A drill dive is where we intentionally charge the mouthfill at a shallow depth, usually at the surface or around 5 metres. The goal isn't to go deep. The goal is to practise the mechanics of charging, and using the mouthfill in an environment that is easy to repeat and easy to troubleshoot, learn and repeat without fatigue.

These dives are also extremely useful for calculating your Mouthfilll ( How Deep Will Your Mouthfill Take You?).

Mouthfill Calculator Tool

Surface Charges

A surface charge is one of my favourite coaching tools.

Even for elite professional freedivers, a surface charge should generally run out somewhere around 35 metres. The reason is simple: between the surface and 35 metres, we pass through enormous pressure changes and the stored air is compressed fast

Because of this, I often ask new students to perform surface charges. If someone reports that they comfortably reached 35, 40, or even deeper on their very first attempt, alarm bells immediately start ringing.

In most cases, they're not actually using a mouthfill at all. They're reverse packing.

A good way to check this is to repeat the dive on FRC. If the results suddenly change dramatically, it's a strong indicator that you were reverse packing on full lungs. On an FRC dive, the lungs reach their Residual Volume much sooner, making reverse packing significantly harder.

5-Metre Charges

Another drill you'll probably do with me countless times, especially if you're doing remote coaching, is the 5-metre charge.

These dives are performed both on full lungs and on FRC so we can compare the data.

A 5-metre charge can be surprisingly effective. For some divers with excellent technique, it can take them beyond 50 or even 60 metres.

Why? Because you've already descended below the surface and bypassed some of the largest pressure changes. The air stored in the mouth therefore lasts longer, giving you both more equalisations and more available depth.

Using Drill Dives to Calculate Your Mouthfill Factor

The real value of surface and 5-metre charges isn't just practising the technique. They also give us useful data.

By comparing how deep your mouthfill takes you from different charging depths, we can calculate your Mouthfill Factor and start building a picture of how efficiently you're using the air you've stored.

This information becomes even more valuable when we compare it against your actual depth dives.

Why Are Real Depth Dives Often Worse?

One of the most common things I see in coaching is that a diver's Mouthfill Factor during drills is often better than it is on real depth dives.

Why?

Because depth adds pressure, both physically and mentally.

During a simulation dive, you're usually relaxed. There's no target depth to chase, no expectations, and very little stress. You're simply focusing on taking and managing the mouthfill.

A real depth dive is different.

You're thinking about your performance, your target depth, your technique, your turn, and everything else happening during the dive. All of this increases cognitive load and often reduces relaxation and body awareness.

As soon as tension creeps in, the quality of the mouthfill usually suffers.

Read more on this topic ( why do i swallow my Mouthfill )

Finding Your Sweet Spot

Charging the mouthfill between approximately 10 and 25 metres is often the most challenging part of learning the skill.

The goal isn't to charge as deep as possible. The goal is to find the depth where you can:

Consistently take a full mouthfill
Stay relaxed throughout the process
Maintain awareness and control of Cheeks-Jaw-Tongue
Manage the stored air comfortably during the rest of the descent (Mouthfill Management)

For some divers this might be 10 metres. For others it could be 15, 20, or even deeper.

There is no perfect charging depth that works for everyone.

The best charging depth is simply the deepest point at which you can still take a full, relaxed, and manageable mouthfill every single time.