Freediving for Competitive Swimmers: The Breath-Hold Edge That Most Coaches Miss

Every competitive swimmer knows the feeling: you push off the wall, go into the dolphin kicks, and the underwater phase is the fastest, most effortless stretch of the entire lap. For a brief moment, there is no resistance, no breath, no struggle — just speed. Most swimmers instinctively want to stay there longer. Most coaches tell them to come up sooner than their body is actually demanding.

The underwater phase of a competitive swim race is consistently the fastest section of any lap — significantly faster than swimming at the surface — yet it remains one of the most systematically undertrained elements in age-group and masters programs worldwide. The swimmers who can hold their breath longer, stay calmer in that underwater stretch, and manage rising CO2 without tensing up are gaining time that cannot be bought through additional aerobic or strength work.

Freediving training is the most direct and physiologically focused way to develop exactly this quality. This article explains the mechanisms, the evidence, and a practical protocol for competitive swimmers who want to unlock an edge that most of their rivals have never considered.

The Underwater Advantage

In competitive swimming, the rules of hydrodynamics favour the diver over the swimmer. A body fully submerged below the turbulence layer — below approximately 60 centimetres — travels through the water with substantially less drag than a body at the surface. The dolphin kick, when performed correctly in the streamlined position, is consistently faster than any surface stroke. Elite swimmers know this instinctively, which is why the fastest freestyle and backstroke performers in the world routinely extend their underwater phases to the legal maximum of 15 metres off each wall.

The data supports this intuition rigorously. A study published in the International Journal of Sports Physiology and Performance in 2014 found that swimmers who extended their underwater dolphin kick phases by just one additional metre improved their 100-metre freestyle times by an average of 0.4 seconds. At the elite level, where international finals are decided by hundredths of a second, this is an enormous margin. At the age-group and masters level, where technical execution is inconsistent, the gains available are even larger.

The limiting factor in most swimmers' underwater phases is not physical strength or stroke mechanics — it is breath-hold tolerance. The swimmer who begins feeling anxious about their CO2 level at the three-second mark will surface earlier than the swimmer who can stay calm and relaxed at five or six seconds without any increase in tension. Freediving trains this capacity more systematically, and at greater physiological depth, than any standard swim program protocol.

The underwater start — the first 10–15 metres off the dive — follows exactly the same logic. The diver who can spend more of that explosive opening phase below the surface, dolphin-kicking in streamline, is handing themselves an advantage that compounds across every race at every distance.

Breathing Pattern Optimization

Competitive swimmers breathe on cycles: every two strokes, every three, every five. Coaches use breathing patterns to balance oxygen supply against stroke disruption — because every time a swimmer turns their head to breathe, it introduces micro-rotation and resistance. The swimmer who can breathe less frequently without discomfort maintains a cleaner, more efficient stroke.

The tolerance for delayed breathing is almost entirely a CO2 tolerance question. The urge to breathe in swimming is not triggered by low oxygen — it is triggered by rising CO2. Swimmers who have a higher physiological threshold for CO2 discomfort can comfortably breathe every five strokes where others need to breathe every two. This is not a matter of willpower; it is a trainable physiological adaptation.

A study published in the Journal of Swimming Research in 2015 demonstrated this directly. Swimmers who incorporated hypoxic set training — sets where breathing was restricted to every five to seven strokes — improved their 200-metre freestyle economy by 7.3% over eight weeks of training, compared to a control group training identically without the breathing restrictions. The mechanism was a measurable increase in the swimmers' CO2 buffering capacity and a reduced sympathetic nervous system response to rising CO2 levels.

Freediving CO2 tolerance training is the purest, most intensive form of exactly this adaptation. A freediving CO2 table — a structured protocol of repeated breath-holds with progressively shortened rest intervals — produces the same physiological stimulus as a full season of hypoxic set training, but concentrated into a few weeks of focused sessions. The swimmer is not practicing a watered-down version of CO2 tolerance. They are training it directly, with full attention, in conditions that demand genuine adaptation.

The competitive swimmer who adds freediving CO2 training to their programme will find that breathing every three or five strokes, which previously required conscious effort and produced discomfort, begins to feel unremarkable. The breathing pattern becomes a choice made from efficiency rather than a compromise between stroke quality and oxygen anxiety.

The Flip Turn Breath-Hold

A technically perfect flip turn requires a brief but physiologically significant breath-hold: from the final stroke before the turn, through the rotation and push-off, into the streamline. In competition conditions, this window is typically 1.5 to 3 seconds — short enough that most swimmers do not consciously think of it as a breath-hold at all.

But the body responds to it as one. CO2-sensitive swimmers approach the wall with a slight background anxiety, tighten their core and neck unnecessarily during the rotation, and push off in a slightly elevated tension state that bleeds into the underwater phase and the first few strokes of the next length. The swimmer who begins the turn composed finishes it composed. The swimmer who begins it slightly anxious about breathing finishes it even more so.

Freediving trains precisely the combination of skills that a perfect flip turn requires: sustained breath-hold under physical effort, with deliberate muscular relaxation and efficient movement mechanics. This is not a metaphorical overlap — it is a functional one. The freediver learning to perform a duck dive efficiently, or to maintain a dolphin kick in streamline for 15 metres, is practicing the same neurological pattern that the swimmer needs at every wall.

The training effect accumulates across both contexts. A swimmer who has completed fifty freediving pool sessions in which they routinely hold their breath for 30 to 60 seconds while performing physical movement will find that a 2-second breath-hold at the turn wall registers as physiologically trivial. The anxiety response that previously degraded their technique at that moment simply does not fire.

Lung Volume and Buoyancy Control

Body position in the water is partly a stroke mechanics question and partly a buoyancy question. A swimmer with greater lung volume — specifically, greater functional residual capacity, the volume of air remaining in the lungs at the end of a normal exhale — sits higher in the water relative to their skeletal density. This reduces frontal drag and improves streamline position at race pace.

Research published in the European Journal of Applied Physiology in 2018 found that competitive swimmers with greater functional residual capacity showed measurably better body position and demonstrated an average 4.1% lower drag coefficient at race pace compared to swimmers with smaller functional residual capacity but matched for other physical characteristics. The authors noted that the relationship between lung volume and body position was especially pronounced during the push-off and glide phases — precisely the underwater phase where freediving training has its most direct application.

Freediving develops two related qualities here. First, it builds genuine awareness of lung volume at different stages of the breath cycle — full, partial, and empty lungs each create different buoyancy and require different adjustments. Freedivers learn to control and sense this with precision. Second, extended breath-hold training does appear to produce modest increases in total lung capacity and vital capacity over time, through the mechanical stretching of lung tissue that repeated full-capacity breaths and extended holds induce.

For competitive swimmers, this translates to a better understanding of how to maximise the natural buoyancy advantages of their lung volume during the phases of each lap where it matters most.

Stress Management in Racing

The physiology of race-day stress is well understood and largely consistent across athletes. In the minutes before a race, adrenaline and cortisol elevate, heart rate climbs, breathing shifts upward into the chest, and the body enters a state of sympathetic nervous system dominance. This is useful — it mobilises energy and sharpens alertness. But it also has a direct cost in the water: chest breathing reduces tidal volume efficiency, elevated heart rate increases oxygen demand at rest, and the physical tension associated with sympathetic arousal degrades streamline position and stroke mechanics.

The consequence is visible in race footage. Many competitive swimmers at all levels show visibly degraded technique in the first 25 metres of a race compared to their training baseline. They are breathing more, tensing more, and executing less precisely than they are capable of. The anxiety of competition is partly responsible, but the inability to downregulate the physiological stress response quickly once in the water is the mechanism through which it costs time.

Freediving trains the dive reflex — the mammalian physiological response to breath-hold and water immersion, which is the direct physiological counterpart of the fight-or-flight response. The dive reflex is parasympathetic: it reduces heart rate, slows metabolic rate, and induces a state of calm focused attention. Trained freedivers enter the water and within seconds experience a measurable drop in heart rate and a shift toward the calm, composed physiological state that produces their best performance.

Competitive swimmers who have incorporated regular freediving practice report entering the water for races noticeably calmer than before, and maintaining their technique further into the race before the accumulation of physical stress begins to show. The mechanism is the same dive reflex, which the freediving practice has trained to activate quickly and reliably on water contact.

Open Water Swimming

The freediving-to-swimming transfer is even clearer for open water swimmers, triathletes, and ocean racers. Open water swimming introduces variables that pool racing never presents: wave interference, salt water, current, crowded starts, and occasional submersion of the head by waves or contact from other swimmers.

A study published in the International Journal of Aquatic Research in 2019 found that open water swimmers who had integrated breath-hold training into their preparation reported significantly lower panic responses to unexpected wave interference and involuntary head submersion compared to swimmers with equivalent fitness but no breath-hold training. The breath-hold practitioners maintained composure and stroke efficiency under conditions that caused the control group to lose technique and increase perceived exertion significantly.

For triathletes competing in Phuket and across Thailand — where ocean swims in the Andaman Sea are a regular feature of the race calendar, and where Phuket's own Blue Lagoon Triathlon and regional events draw hundreds of competitors annually — this is directly relevant. The Andaman Sea offers extraordinary open water swimming, but also chop, current, and conditions that reward calm heads and breath control. Freediving training is the most direct path to developing those qualities.

Marathon swimmers and ocean swimmers similarly benefit. Extended open water efforts involve minutes of rhythmic breathing under sustained physical stress, with no walls to rest at and no lane ropes to orient by. The swimmers who manage CO2, conserve energy, and stay composed over long distances are those whose breath-hold training has given their nervous system a baseline of calm that pool-only training rarely produces.

Hypoxic Sets vs. Freediving

Most competitive swim programs use hypoxic sets — sets in which breathing is restricted to every 5, 7, or even 9 strokes — as a form of CO2 tolerance training. The logic is sound: if you train the body to tolerate higher CO2 during swimming, breathing frequency can be reduced in races without performance decline.

But there are significant limitations to this approach. Hypoxic sets are performed at swim-specific intensities and stroke mechanics, which means the CO2 stimulus is diluted by the competing demands of technique maintenance and aerobic effort. Coaches must manage the intensity carefully to avoid technique degradation, which means the CO2 training stimulus is often lower than intended. Athletes who find the sensation extremely uncomfortable tend to unconsciously reduce effort to reduce CO2 production, which defeats the purpose of the set.

Freediving CO2 tables isolate the CO2 stimulus completely. The diver is still, or performing a controlled physical effort, with no competing technical demands. The attention is entirely on managing the physiological response. The CO2 accumulation can be precisely controlled through the table design. Feedback — how the diver responds to the urge to breathe — is immediate and unambiguous.

The result is that four weeks of structured freediving CO2 training typically produces adaptations equivalent to a full macrocycle of hypoxic set training — because the stimulus is cleaner, more intense, and more precisely targeted. Swimmers who add freediving to their training are not supplementing their hypoxic sets; they are doing what hypoxic sets were designed to achieve, but doing it better.

The combination of both approaches — freediving CO2 training off-season, hypoxic sets in-season to maintain and apply the adaptation under sport-specific conditions — is probably the most powerful protocol currently available to competitive swimmers who want to optimise this quality.

The Masters Swimming Opportunity

Masters swimming is one of the fastest-growing competitive swimming markets globally, with athletes competing well into their seventies and eighties in age-group categories that grow every year. Masters swimmers bring decades of technique and competitive experience. They also face the biological reality that lung function — specifically vital capacity and breath-hold tolerance — declines with age in untrained populations at approximately 1% per year from the early thirties onward.

The word "untrained" is doing significant work in that sentence. Lung function decline with age is not inevitable in the same way that muscle atrophy is. It is substantially driven by reduced mechanical loading — fewer full-capacity breaths, less use of the diaphragm at full range, reduced respiratory muscle strength. All of these are directly reversible through freediving training.

Masters swimmers who add freediving twice a week as a complementary practice maintain lung function that would otherwise decline. They also maintain or improve the CO2 tolerance and breath-hold performance that supports their underwater phases — the phases that, proportionally, become more important to race time as surface-stroke speed declines with age. For a masters swimmer, a longer, more controlled underwater phase is a higher-value technical investment than for a younger athlete with more explosive surface speed.

The freediving protocol for masters swimmers is exactly the same as for younger athletes, with attention to appropriate load management: static CO2 tables before water sessions, progressive dynamic apnea in the pool, and careful monitoring of recovery. The adaptations accumulate over the same timescale and are at least as durable.

Practical Protocol for Competitive Swimmers

The following protocol is designed as a complement to an existing swim training programme. Water sessions require a qualified buddy or instructor present at all times.

Weeks 1–2: Dry CO2 Tables

Begin with static CO2 tables performed dry, lying down. This removes any water-anxiety variable and allows full focus on the physiological response. Standard table: 8 rounds of 2-minute holds, rest intervals starting at 2 minutes and decreasing by 15 seconds each round. No hyperventilation before holds — two to three calm, full breaths only.

Weeks 3–4: Pool Static and 25-metre Glides

Add pool sessions. Start with static apnea in the water (face down, supported at the surface by a buddy, no swimming). Then add 25-metre breath-hold swims — no kick, arms by the side, pure streamline glide — to train relaxation under movement with breath-hold. Focus is on staying loose, not covering distance quickly.

Weeks 5–8: Extended Underwater Phases and Dynamic Apnea

Integrate the training explicitly into swim practice. Push off each turn with a deliberate extended underwater phase — measure it and extend by half a metre each week. Add 50-metre dynamic apnea (swim with fins or without) to pool sessions to build CO2 tolerance under movement. By week 8, many swimmers will be comfortable holding their breath for 3–4 minutes in static and covering 50–75 metres in dynamic.

In-season maintenance:

Static CO2 tables only, 30 minutes, twice per week. No dynamic apnea in-season unless the athlete is experienced. The goal is to maintain the adaptation without adding recovery burden before races.

What Most Coaches Are Missing

The underwater phase of a race is the fastest part of every lap. It is the section of every race most directly limited by breath-hold tolerance and CO2 management. And it is the section most systematically undertrained in age-group and masters programs, because most coaches have no freediving background and therefore no intuition for how to develop it beyond basic underwater drill work.

Freediving certification — a Wave 1 course takes a weekend — gives competitive swimmers a complete technical and physiological framework for developing their underwater phase. It covers CO2 and O2 physiology, breath-hold technique, safety protocols, and progressive training structures. The certification is internationally recognised, the skills are immediately applicable, and the competitive advantage is technically legal and physiologically sound.

For more on the CO2 tolerance training protocols that underpin this work, see our detailed article on CO2 tolerance training for freedivers. For a deeper look at the breathing mechanics involved, breathing techniques in freediving covers the foundations in full.

If you are based in Phuket or visiting Thailand and want to explore how freediving training can be integrated with a competitive swim programme, get in touch. We work with athletes at all levels and can design a protocol that fits your training calendar.

The underwater phase is waiting. Most of your competitors have not found it yet.