Freediving to 40 Meters: How to Prepare for a Clean and Safe Dive
- Anthony Feoutis
- Jun 8
- 12 min read
How to Become a Fantastic 40-Meter Diver
AIDA & Molchanovs Instructor Trainer
He is the founder of The Depth Collector and VD Freediving Taiwan. With over a decade of experience, he focuses on solving real-world freediving problems, from equalization to depth adaptation, using practical, field-tested methods.
Before You Read This
If you haven’t read Freediving to 30 Meters yet, start there first. It explains the foundation that makes this 40-meter article much easier to understand.
Freediving to 40 Meters: The Depth Where You Stop Guessing
40 meters is one of those depths that changes the way you look at freediving. It is often seen as the upper limit of recreational freediving. It is a common requirement for instructor-level training. It is also the depth where many divers start moving from basic equalization toward more advanced strategies like deep Frenzel, mouthfill, or cheek fill.
For me, the first time I reached 40 meters was a massive deal.
I had worked hard for that number. Really hard.
It was not just “one more depth.” It was the depth that would open the door to my instructor certification. At that stage of my journey, 40 meters felt enormous.
My coach, Julia, had forbidden me to learn mouthfill yet.
Not suggested.
Forbidden.
So I had no choice. I had to master Frenzel properly.
And honestly, that was probably one of the best things that could have happened to me.
I became obsessed with every detail: the different tongue locks, the soft palate, the tiny reverse packs, the timing, the head position, and the changing pressure as I went deeper.
Nothing was random.
I had carefully organized every step of the dive. I was not relying on alarms. I counted my pulls and kicks. I knew where I should be. I knew when I should start my freefall. Around 25 meters, I would stop working and let the ocean do its job.
And still, I was stressed as fuck.
Excited, yes.
But stressed.
Looking back, that stress was clearly a sign that I did not fully trust myself yet. I had prepared the dive, but part of me still needed proof that I belonged there.
That is the funny thing about milestones. Is 38 meters really different from 40 meters?
Sometimes you are ready enough to do them, but not calm enough to fully enjoy them.
I made the dive, and it was easy.
Then I looked at my computer.
39.9 meters.
Julia told me it was the same.
Technically, she was right.
Emotionally, absolutely not.
At that moment in my journey, 39.9 was not 40. I did not want a philosophical discussion about measurement tolerance. I wanted the four and the zero.
So for the next dive, I made sure the line was one meter deeper.
Was that rational?
You tell me :)
But the lesson I take from that experience now is different from the lesson I took back then.
Back then, I thought the achievement was reaching 40.
Now I understand that the real achievement was everything I had built before it: the Frenzel work, all the stretching, the structure of the dive, the technique during every phase, the shallow repetitions, the discipline, the patience to drop the line two meters at a time, and the self-control to make sure I was completely ready at each depth before going deeper.
The 39.9 was just the visible result of all the hours spent preparing for it.
Before You Train for 40 Meters, Your 30 Meters Must Be Solid
Something crucial needs to be understood before we talk about 40 meters.
It will be very hard to reach 40 meters comfortably if your 30 meters are not already solid.
So before going further, I invite you to read the article I wrote about diving to 30 meters. I am saying this because 30 meters is the foundation. If that foundation is unstable, everything you build above it will eventually start shaking and will fall apart.
For this article, I am going to assume a few things.
I am going to assume that you are not discovering the dive as it happens:
You are already a very solid 30-meter diver.
Your Frenzel is clean.
Your dive is organized.
You have accuratly set your neutral buoyancy.
You know where your freefall starts.
Your technique is good, no matter which discipline you prefer: FIM, CWT, CWTB, CNF, whatever makes your little freediver heart happy.
You know how to use the change in buoyancy to save energy
You have worked on your CO₂ tolerance, either dry or in the pool.
You have already started stretching your diaphragm, ribcage, and breathing muscles.
All of that is what makes you a fantastic 30-meter diver.
And if you are already that fantastic 30-meter diver, then yes, you are ready to approach the next challenge: becoming a fantastic 40-meter diver.
Not surviving 40.
Reaching 40 properly.
Big difference.
Step 1: Prepare Your Body for Pressure
The first rule is simple.
Prepare your body before asking it to accept more pressure.
Diving deeper than 30 meters pushes you and your diaphragm into new territory.
At these depths, depending on your lungs and flexibility, you start moving beyond residual volume. Your lungs become very small. Two oranges. Two lemons. Two little grapefruits. Pick your favorite citrus fruit.
The point is simple: your lungs are compressed, your diaphragm moves up into your chest, and the pressure is no longer a pretty diagram in a freediving manual; you feel it in your flesh.
This is why diaphragm and ribcage flexibility become so important.
If your diaphragm is stiff, if your ribcage is tight, if your breathing muscles are locked, the pressure will feel much more aggressive. You may feel that vacuum sensation in the chest. That pull. That tightness. That famous “ouch” everybody talks about.
And once that happens, the domino effect begins.
Tension rises. Relaxation drops. Oxygen consumption increases. More CO₂ is produced. The urge to breathe becomes louder. Relaxation becomes even harder.
And suddenly, the dive that was supposed to be smooth becomes a whole dramatic underwater soap opera because you were too lazy to wake up 10 minutes earlier and follow my fantastic diaphragm stretching routine.
Yes, I am judging you a little.
Not too much.
But a little.
I am not a huge fan of relying only on Uddiyana Bandha for this kind of work. It has value, of course. But for deep freediving preparation, you need to hold and explore the stretch longer, more progressively, and with more control. Very quickly, Uddiyana alone reaches its limit.
Your diaphragm flexibility does not only affect how pressure feels.
It can also affect your equalization.
When the lungs compress, and the diaphragm is pulled upward, the resulting negative pressure can affect your glottis. If you are tense, stiff, or badly coordinated, the pull from the chest can make it harder to keep the glottis closed.
And if the glottis opens at the wrong time, guess what happens?
You leak the air from your mouth back into your lungs.
Goodbye beautiful equalization plan.
Hello frustration.
So when I talk about diaphragm flexibility, I am not talking about some nice little wellness stretch with your mandala bedsheet hanging behind you to look spiritual on Instagram.
I am talking about performance.
Comfort at depth. Pressure adaptation. Equalization control. The ability to keep the air where you need it.
In your mouth.
Not sucked back into your chest like your lungs are stealing from you.
So Step 1 is simple: stretch your diaphragm and ribcage every day.
Not once before the dive.
Not when pressure starts feeling uncomfortable.
Every day.
Because flexibility is something you build before you need it.
Step 2: Go Slow, You Little Depth Addict
If you are truly ready, the progression from 30 to 40 meters can happen quite fast.
But that is not an excuse to drop the line too deep, too fast.
Give the ocean the time to transform you.
And I do not mean that as a cute metaphor. The ocean is literally changing how your body understands pressure.
Your diaphragm, lungs, trachea, and nervous system all need repeated exposure before the new depth starts feeling normal.
If you rush, you increase the chance of bad adaptation, chest discomfort, messy equalization, injuries and a beautiful mental block that may take months to undo.
Very impressive.
Very unnecessary.
So progress slowly.
Start with 32 meters.
Do the dive.
If it feels comfortable, repeat it.
Then, instead of immediately dropping the line deeper, repeat the same depth and add a small 5-second hang. 5 little seconds.
If that feels easy, repeat the dive again and add a 10-second hang. No need for more.
This does not all need to happen on the same training day. It depends on how you feel, how clean the dives are, how your equalization behaves, how relaxed your body is, and how much your nervous system trusts what is happening. It is completely fine to spread these dives over two sessions or more.
Then you can move to 34 meters.
Same idea.
Do the dive. If it feels clean and comfortable, repeat it with a 5-second hang. If that feels easy, repeat it with a 10-second hang.
Then 36 meters.
Then 38.
Then 40.
Little by little.
The small hangs are useful for two reasons.
First, they build confidence. A 32-meter dive with a 10-second hang simulates the dive time of a deeper dive, roughly around 37 meters. So when you move to 34 meters, your mind already knows you can handle the dive time. Suddenly, 34 does not feel like a big dramatic event anymore.
Pfff. Piece of shrimp cake.
Second, those hangs give your body more time to adapt to the new pressure. You are not just touching the depth and running away. You are staying there calmly for a short moment, letting your body and nervous system understand the environment.
During the hang, scan your body.
Jaw. Tongue. Throat. Shoulders. Chest. Diaphragm. Belly. Legs.
Release whatever does not need to be tense. Or, as Alexey Molchanov once told me: embrace the pressure.
Many equalization problems stem from tensions we are not even aware of. The body scan helps you notice where you are holding unnecessary effort, and once you notice it, you can start fixing it.
If any dive becomes hard, do not force it.
Rest. Remember that resting is also training. And then go back to the previous depth, the easy one. Repeat it a few times. Make it clean again. Then drop the line deeper when your body is ready.
That is how you progress.
Always in control.
Freediving is not a sprint.
So Step 2 is simple: use your brain. Give your body and mind time to adapt. Perfect your relaxation. Refine your equalization. Keep tuning your technique.
Step 3: Use FRC to Teach Your Body Pressure
FRC stands for functional residual capacity. It is the amount of air left in your lungs after a normal, relaxed exhalation, roughly around 50% of your total lung capacity.
A normal breath in.
A normal, relaxed breath out.
Hold.
Dive.
Easy.
FRC diving is not about numbers on your computer. There is no such thing as an FRC PB.
That is ridiculous.
FRC is there to simulate depth, teach your body pressure, and let you work on equalization below your usual full-lung residual volume.
For a 40-meter goal, you do not need deep FRC dives.
You do not need 25 meters.
You do not need 30 meters.
Absolutely not.
You need to pass 10 meters cleanly, then slowly build your equalization and pressure adaptation to a slightly deeper depth. Fifteen meters is already very good. Twenty meters should be considered more than enough for this goal.
Let’s take Mike.
Because Mike is always useful for these things.
Mike has a 6-liter total lung capacity. If he takes a full breath and dives down, his lungs are roughly 3 liters at 10 meters, 2 liters at 20 meters, and 1.5 liters at 30 meters.
That means, around 30 meters, Mike reaches his residual-volume zone.
Now Mike does a proper FRC dive. Since FRC is roughly 50% of total lung capacity, he starts the dive with about 3 liters of air in his lungs.
At 10 meters, those 3 liters are compressed to about 1.5 liters.
Same lung size as his 30-meter full-lung dive.
Boom.
That is the magic of FRC.
By doing a clean FRC dive to 10 meters, Mike is already exposing his body to a lung volume similar to what he experiences around 30 meters on a full-lung dive.
If he wants to prepare for 40 meters, he does not need to be a hero. He needs to slowly become comfortable passing that 10-meter mark on FRC, then build carefully from there.
FRC is pressure education.
Not ego.
Not numbers.
Not a stupidity contest.
Pressure education.
One important warning: FRC can cause injury if you treat it like a game.
At this depth, blood shift becomes part of the adaptation process. Your body starts moving more blood toward the chest to help protect the lungs under compression. In simple terms, the small blood vessels around the lungs fill with more blood than they are used to and help support the lung tissue under pressure. But those vessels still need time to adapt. If you rush the progression, force the dive, contract hard at depth, or continue after discomfort appears, you increase the risk of a lung or tracheal squeeze.
So FRC training must be slow, conservative, and controlled.
Use free immersion for these dives. It lets you control your speed, stop immediately, and come back up gently if something feels wrong.
Respect two clear signals.
Chest pressure: stop for 5 seconds (no need for more), relax, soften the diaphragm. If the pressure does not disappear quickly, comeback up gently.
Failed equalization: stop immediately. Do not force it. Wait 5 seconds (no need for more) and try to understand what mistake you are making. Take the information, then come back up calmly.
I prefer to make FRC its own training session rather than use it as a warm-up before a serious deep dive. After FRC work, the blood shift and chest sensations can make the next full breath feel less comfortable. And no, thank you. Before a deep dive, I want a full, easy, comfortable breath. I want the inhale to feel clean, open, and calm, not like my chest is still processing the previous dive.
A full FRC training session should include 6 to 8 FRC dives at most, and fewer if you feel tired.
FRC training will help prepare you beautifully for your 40-meter dive.
Step 4: Build Equalization Before You Need It
I reached my first 40 meters with Frenzel.
No mouthfill.
Just that good old Frenzel.
But hey, not lazy Frenzel.
Not the vague “yeah yeah, I can equalize” kind of Frenzel.
I mean proper Frenzel. The detailed kind. The kind where you actually understand what your tongue is doing, what your soft palate is doing, what your glottis is doing, and why the whole thing sometimes works beautifully and sometimes does not.
As I said earlier, Julia had forbidden me to learn mouthfill before that.
At the time, I probably thought it was unfair.
Of course I did.
I wanted the cool technique. The thing deep divers were using.
But she was right.
Forcing me to stay with Frenzel made me precise.
And honestly, that gave me something much more valuable than a shortcut.
It gave me control.
That is the point I want you to understand.
Equalization should be built before you need it.
Not improvised at 35 meters while your little freediver soul suddenly remembers it has a body.
Too late, my friend.
If you want to use mouthfill later, great. Mouthfill is beautiful. Mouthfill is powerful. Mouthfill can make deeper diving much easier, but only if you have already mastered Frenzel.
But mouthfill should not be something you first understand on a deep dive.
Train it dry. Train it shallow. Train it on FRC exercises. Train it until the coordination becomes boring.
Because boring is good.
Boring means your nervous system is no longer treating the technique like a new problem.
Boring means you can think about the dive instead of thinking about the technique.
And that is exactly what you want.
The same applies to Frenzel.
A lot of freedivers want a new technique when what they really need is better control of the technique they already have.
Master your skills first.
Then, when you finally need it for a new depth, it should feel like something you have done a thousand times already.
Because ideally, you have.
The 40-Meter Checklist
Before you seriously attempt training for 40 meters, check the basics.
Can you repeat clean 30-meter dives without drama? YES/NO
Can you equalize with perfect control? YES/NO
Can you start your freefall exactly where you planned it, every single time? YES/NO
Can you keep your body relaxed when pressure starts changing? YES/NO
Can you handle the expected longer dive time? YES/NO
Good.
Now we can talk.
The simple checklist looks like this:
Solid 30-meter dives
Daily diaphragm and ribcage stretching
Slow progression: 32, 34, 36, 38, 40
Small hangs for time, confidence, and adaptation
FRC training sessions to work on depth adaptation, Frenzel or mouthfill.
Clear dive organization from the surface to the recovery breath.
That is the recipe.
And if one ingredient is missing, do not pretend the cake will be amazing.
Fix the ingredient.
Then go deeper.
Train Deeper With The Depth Collector
If you want to go deeper into this progression, I explore equalization, CO₂ tolerance, dry training, physical preparation, recovery, and long-term adaptation in much more detail in The Depth Collector series.
This article is one part of the system. The books are where I organize the full training philosophy: how to build depth step by step, without turning every dive into a stupid little war against yourself.
Final Thoughts: 40 Meters Is Built Before the Dive
My first dive to 40 meters, or, if I am being painfully honest, 39.9 meters, remains one of the most memorable dives of my freediving journey.
Of course, there have been many others since then. Deeper dives. Better dives. Cleaner dives.
But this one opened my professional path.
Not just because of the number, but because of everything I had put into it: the training, the discipline, the stretching, the Frenzel work, the patience, and the thousands of tiny details that nobody sees when the dive computer finally shows the result.
That dive gave me the desire to keep going, to keep learning, and to keep diving deeper with the lessons I had earned along the way.
The next step was 50 meters.
And that new path did not go as planned.
I will tell you more in the next article.
Train smart, dive deep, and stay safe.
Sea you.
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