O₂ Tables for Freediving: Extend Your Breath-Hold

O₂ Tables for Freediving: Extend Your Breath-Hold

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O₂ tables for freediving train your body to keep working as oxygen runs low — the adaptation that lets deeper spearfishers extend their bottom time without panic. Where a CO₂ table holds the hold steady, an O₂ table makes each hold longer while the rest stays fixed, walking you progressively toward your limit. That's powerful, and it's also why O₂ tables demand more respect and a spotter. Here's how they're structured, a sample table to work from, what a session feels like, the non-negotiable safety rule, and a safe way to progress over time.

What an O₂ Table Trains

An O₂ table accustoms your body to a lower level of oxygen. By the late rounds you're carrying a real oxygen deficit, which nudges your body's coping mechanisms — the dive reflex, spleen contraction, and tolerance to hypoxia — to adapt. The payoff is a longer usable hold and more composure deep in a dive, when oxygen is genuinely getting scarce.

Because it deliberately pushes toward your limit, the O₂ table is the higher-risk half of the system described in Breath-Hold Tables: The Complete CO₂ & O₂ Guide. Treat it accordingly.

How an O₂ Table Is Structured

The defining feature: the rest stays the same every round, while the hold gets longer. With a constant rest, you start each hold reasonably recovered on CO₂, but the lengthening holds drive your oxygen progressively lower across the set. The last round is close to a maximal effort.

A standard table runs about six to eight rounds. Holds typically start around half your max and climb toward 80–90% of it by the end.

A Sample O₂ Table You Can Use

This example assumes a relaxed max hold of about 3:00, with a constant 2:00 rest. The rest never changes; the hold climbs.

RoundRest (breathe-up)Hold
12:001:30
22:001:45
32:002:00
42:002:15
52:002:30
62:002:40

Set these holds from your own recent max rather than copying the figures — the arithmetic is in How to Make a Breath-Hold Table, Step by Step.

Safety Warning O₂ tables walk you toward your oxygen limit by design, so blackout is a real risk. Do them dry or in a supervised, stationary pool — never in open water, never alone. The same physiology that ends an O₂ table badly is what causes shallow water blackout; read that guide before you start.

What a Session Actually Feels Like

An O₂ table feels very different from a CO₂ table. The early rounds are comfortable, but unlike a CO₂ set, each round gets noticeably longer, so the contractions arrive later and then last longer with every round. By the final one or two holds you're deep in oxygen debt: contractions are heavy, your focus narrows, and the temptation to cut the hold short is strong. This is exactly where a spotter matters most — the last round is the riskiest, and it's also where loss of motor control can appear without much warning. Finish on a hold you completed cleanly, not on one you barely survived.

"O₂ tables are the one set I never run without a buddy at arm's reach. The day you feel invincible on them is the day they bite." — Fishes One Hook, dive log #96

The Non-Negotiable Spotter Rule

If a CO₂ table is the one you can do alone on the living-room floor, the O₂ table is the one you never do without a trained spotter. Their job is to watch you — your face, your hands, your recovery — not their own stopwatch. Loss of motor control ("samba") and full blackout can arrive with little warning in the final rounds, and in water they are silent and fatal within seconds.

Pro Tip Brief your spotter on the recovery protocol before you start: tap signal at the end of each hold, "are you okay" check, and a clear plan for supporting your airway if you samba. A spotter who doesn't know the signs isn't a spotter.
A freediver floating face-down in a pool while a trained spotter watches closely at arm's length
Wet O₂ tables are spotter-only work: the buddy stays at arm's length, eyes on the diver throughout.

Progressing Your O₂ Table Over Time

Progress slowly. As your max hold grows, recalculate the table from the new number rather than just tacking time onto the last round. A safe progression over a training block might look like this:

WeeksAdjustmentGoal
1–26 rounds, holds 50% → 75% of maxComfortable; clean recovery every round
3–4Add a 7th round; final hold ~80%Heavy contractions only in the last round
5–6Re-test max; rebuild table from new numberKeep the relative effort, not the raw times
7–8Nudge final hold toward 85%Composure under real oxygen debt

Add a round, or nudge the final holds up by ten to fifteen seconds, every couple of weeks — not every session. If the last round starts producing light-headedness or a samba, back off; that's overreaching, not progress. When basic O₂ tables plateau, the hybrid and progressive variants in Advanced Apnea Tables: Hybrid, Ladder & Pyramid are the next step, and the right weekly spacing is covered in how often to do CO₂ and O₂ tables.

Early access We're building Spira — a free AI apnea-table app that generates your O₂ and CO₂ tables and times every round, with premium weekly-plan generation and extra table types. It's in development; join the early-access list.

Frequently Asked Questions

Frequently asked
Are O₂ tables more dangerous than CO₂ tables?
Yes. O₂ tables deliberately drive your oxygen low and approach your limit, so blackout is a genuine risk. They should only be done dry or in a supervised pool, never alone and never in open water.
How long should the holds be in an O₂ table?
Start the first hold around half your relaxed maximum and climb toward 80–90% by the final round. Always derive the numbers from a recent, honest max hold rather than copying a generic table.
Can I do an O₂ table by myself?
Never in water. A dry O₂ table can be done solo only if you stay well back from your limit, but because the table's purpose is to approach that limit, a trained spotter is strongly recommended for any meaningful O₂ session.
How often should I train O₂ tables?
Once or twice a week is plenty, and never on the same day as a CO₂ table. The oxygen stress they create needs full recovery to produce adaptation.
Why is the last round of an O₂ table the most dangerous?
The final, longest hold puts you in the deepest oxygen debt of the session, which is when samba and blackout are most likely. Always have a spotter for it, and stop if your recovery isn't clean.
Contributor

Lucas Davis

A Fishes One Hook contributor — logging dives, testing gear, and writing it all down between surface intervals.

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