Underwater Squad
Cheat Sheet
Everything you need to know about CO2 tolerance training. What it is, how to build your own table, and how to progress safely over time.
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A CO2 table is a structured series of breath-holds designed to build your tolerance to rising carbon dioxide. The gas responsible for the urge to breathe and those diaphragm contractions.
The core idea of a CO2 tolerance table is simple. Between rounds, your rest time is not long enough for CO2 levels to return to baseline. So every breath-hold starts with already elevated CO2. That's how you build tolerance.
The urge to breathe comes from rising CO2, not lack of oxygen. By repeatedly starting holds with elevated CO2, you train your body and mind to stay calm with sensations most people panic at.
In a CO2 table you primarily train tolerance to CO2. In an O2 table you primarily train your threshold to low O2 (hypoxia). The rest is long enough for CO2 to return to baseline, but the repeated holds drive O2 down.
Here are 3 different types of CO2 tables as an example. These are not the only ones. For beginners, you start with the 10x 0:30 and tweak from there. If you think you can do 3x 2:00, tweak from there instead. Eventually you do the 2x 1:30. These tables are interchangeable. You can rotate between them and tweak them to your level.
Note: not every breath-hold table is a CO2 table. A full training program also includes other types like progressive breath-hold tables. This document is specifically about CO2 tables.
Ten rounds of 0:30 holds with just one breath between each. Short holds keep this manageable while the single breath keeps CO2 elevated throughout.
Keep one breath between holds. Increase the hold: 0:30 → 0:45 → 1:00.
Five rounds with timed rest intervals. Here you have more time in between but also longer holds.
Keep the hold at 2:00. Decrease the rest in between over time: 1:30 → 1:15 → 1:00.
Five rounds of 1:30 holds with just two breaths between each. Longer holds combined with very limited recovery.
Keep two breaths between holds. Increase the hold: 1:30 → 1:45 → 2:00.
CO2 training is as much mental as physical. For beginners, even more so.
The big mistake beginners make is thinking it's about the rest in between. It's not. The rest intervals are not what moves the needle. What moves the needle is the mental shift that makes you relax when rest gets shorter.
Beginners focus on "how much time should I have between holds?" Wrong focus. The right focus is: "how can I relax even more when I do these tables?"
Dry training? Always lie down on a bed or sofa. Never stand. You could faint and hit your head. Also no facial gear when training alone. No nose clip, no mask. Nothing on your face.
In water? Always have a trained buddy. A lifeguard does not count. Neither does a family member, a partner, a friend, or a random stranger. It needs to be a trained freediver.
One table per session. Do one table, then call it a day. We go for sustainability and continuous practice over time, not too much in one day. Doing more stresses your central nervous system.
Don't over-breathe during rest periods. Calm, diaphragmatic breaths only. Hyperventilating defeats the purpose.
Keep it manageable. Aim for moderate intensity, not high intensity. High intensity stresses the central nervous system and creates a negative mental feedback loop that makes the practice unsustainable.
Max 2–3 CO2 sessions per week. You can train more often, but not with CO2 tables every day. Mix in light breathwork or normal sessions in between.
Freediving is not about chasing numbers. It's a tool for self-discovery. Holding your breath teaches you to become comfortable with the uncomfortable. That translates directly into life.
CO2 tolerance is not just a physical skill. It's a metaphor for handling discomfort in any situation. Everything else flows from that.
CO2 tolerance starts with breathing correctly. Not with holding your breath.
The 6-Week Breather Challenge is my foundational breathwork course. One video per day. 15 minutes per session. That's where you start.
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