Gert Leroy
Freedivers, spearos & mermaids

Freediving breathwork and CO2 tolerance training

A longer breath-hold isn't about bigger lungs. It's about CO₂ tolerance and staying calm when the urge to breathe hits. Train it from home, on the floor, in 15 minutes a day. No water needed.

1.5M subscribers on YouTube Former national record holder 15 min a day
Gert Leroy, freediving instructor and breathwork coach, floating at the surface
Gert Leroy, freediving instructor and breathwork coach, floating at the surface

The real limit

Most people fight the discomfort. This trains you to sit with it.

Your hold almost never ends because you ran out of oxygen. It ends because carbon dioxide builds up, your diaphragm starts contracting, and your body insists you have to breathe right now. That signal is a chemical alarm, not a countdown — and how you respond to it is trainable.

Freediving breathwork

The breathing that makes a longer hold possible

Breathwork for freedivers is not the fast, intense breathing you'll find in wellness classes. Here it has three jobs: calm the nervous system before the hold, fill the lungs without tension, and recover cleanly afterwards. Done well it drops your oxygen consumption before you've held a single second.

Preparation — ten minutes

The breathe-up

Two minutes of tidal breathing — normal, light, unforced, with a soft long exhale. The mind slows, the heart rate drops, the chest and shoulders release. Then one final breath: lungs filled completely, without straining. Tension in the chest at that moment costs you a minute later on.

Recovery breathing

Four big active recovery breaths when the hold ends — every time, even when you feel fine. Build the habit while holds are short, so it's automatic once they're long. Recovery breathing is a safety skill, not an afterthought.

One thing to be clear aboutHyperventilation — fast, deep breathing to "get more air" before a hold — does not add meaningful oxygen. It strips out CO₂, removing the warning signal that tells you to breathe. In water, that is the classic route to a blackout. Never over-breathe during rest periods either. Practise dry, and never hold your breath in water alone.

The exercises that build the hold

Fifteen minutes a day beats two long sessions a week. Breathwork is a nervous-system skill, and nervous systems learn from frequency. Next: CO₂ tolerance and the tables.

Watch first

Every breath-hold follows the same five stages

Preparation, breathe-up, relaxation, contractions, recovery. Most people panic mid-hold because they don't know which stage they're in. When you can name it, the sensation stops feeling like an emergency.

Gert walks through all five stages and what happens in your body at each one.

Read the full stage-by-stage breakdown ›

What's inside

One classroom, one progression

1. Breather Challenge

Six weeks, 15 minutes a day. The breathing that makes longer holds possible, before you chase a number.

2. Breath-Hold Builder

Progressive tables that take you toward the five-minute mark, step by step.

3. Advanced Toolkit

Breathing protocols that keep raising CO₂ tolerance without holding your breath at all.

Plus the exercise library, weekly live training with replays, member training logs and the safety rules.

Inside the Underwater Squad classroom: onboarding, Ultimate 1, Ultimate 2, advanced breathwork, live replays and the exercise library
Inside the Underwater Squad classroom: onboarding, Ultimate 1, Ultimate 2, advanced breathwork, live replays and the exercise library

Recent PBs from the Squad

What a few focused weeks looks like

2:10
0:50 → 2:10 in 26 daysEmma P. · new to breath-hold
4:08
2:03 → 4:08 in 45 daysHassan R. · spearo
5:04
2:45 → 5:04 in 62 daysChris H. · returning freediver

See what members are posting inside the community ›

Your coach

I'm Gert Leroy

Freediving instructor, former national record holder, 1.5 million subscribers on YouTube. The people who improve fastest are the ones who learn to relax first — calm first, numbers second. Then the numbers come anyway.

More about Gert and the method ›

Start your first breath-hold week

Join the Squad and follow the 6-week Breather Challenge from day one. Fifteen minutes a day, dry, at home. Seven-day free trial.

Join with the 7-day free trial