Open Water IsDecision-Making Under Uncertainty

Pool swimming is a controlled environment. The lane line protects the swimmer from chaos. Temperature is fixed. The wall arrives every 25 or 50 meters. Other swimmers stay in their lanes. The variables are essentially the swimmer, the clock, and the stroke. The question being tested is mostly physiological, namely how fast can you cover a known distance under known conditions.

Open water removes the lane. The water moves. The temperature varies. The course is marked only by buoys you have to find while breathing. Other swimmers are in your space. The pack reorganizes every few minutes. The variables are no longer the swimmer and the clock alone. The variables now include the current, the chop, the contact, the sighting line, the pack, the pace strategy of every other swimmer in the pack, and the swimmer’s own fatigue clock running in the background. The question being tested is no longer only physiological. The question is whether the swimmer can keep making good decisions while tired.

This is the proposition the essay argues. Open water swimming is endurance plus decision-making under uncertainty. Triathlon is the same problem expanded across three disciplines under escalating fatigue. The pool athlete who has never raced in open water has trained the engine but not necessarily the decision-making system that has to operate the engine when the environment refuses to cooperate. I argue, on the basis of convergent peer-reviewed literature on drafting energetics, fatigue effects on cognition, heat-stress effects on pacing, and triathlon-specific pacing factors, that open water is a strong foundation for triathlon. I do not argue this is proven. The direct comparison, namely whether open water-trained athletes adapt to triathlon faster than pool-only athletes, has not, to my knowledge, been tested in a controlled study. This essay treats the proposition as a hypothesis worth taking seriously, supported by the literature it cites and by my own racing experience, which I will identify clearly when I draw on it.

Pool swimming asks how fast you can swim. Open water asks how well you can decide while swimming. Triathlon asks how well you can decide twice more, with the consequences of every earlier decision still in your legs.

The pool removes the variables. Open water restores them.

The architecture of pool swimming is designed to control variation. The water temperature is regulated, typically between 25 and 28 degrees Celsius for competition. The lane line eliminates contact with other swimmers. The black T at the end of the lane removes navigation. The wall arrives at predictable intervals. Surface chop is essentially zero. Visibility is perfect. The starting block is a known platform. The swimmer’s job inside this architecture is to execute a rehearsed stroke under known conditions.

Baldassarre, Bonifazi, Zamparo, and Piacentini, in their 2017 review of open water swimming performance published in the International Journal of Sports Physiology and Performance, identify the structural difference clearly. Open water races, they write, may be characterized by extreme environmental conditions including water temperature, tides, currents, and waves, and these conditions have an overall impact on performance influencing tactics and pacing. The variables that pool swimming protects against are exactly the variables that open water restores.

The U.S. Masters Swimming organization, in its triathlon-swimming education materials, describes the start of an open water race as a chaotic moment in which getting kicked in the face, chest, or gut may take the wind out of you, cause you to panic, and in some cases cause real injury. The triathlon-coaching literature broadly characterizes the swim start as a washing machine of arms, feet, and elbows, namely a mass-start environment that is qualitatively different from a pool race. The athlete who has only trained in lane lines has not trained for this environment, and the lack of training shows up not in the engine but in the decision-making.

The decisions an open water swimmer must make in the first ten minutes of a race include the following. Where in the start formation should I line up given my swim ability and my comfort with contact. Should I sprint the first 100 meters to escape the chaos or hold back and find clean water. When I take contact, do I respond with force, with adjustment, or with relaxation. When I sight up and the buoy is not where I expected, do I correct hard, correct slowly, or commit to the new line. When I find feet to draft, do I commit to those feet or look for faster ones. Each of these decisions is being made while the cardiovascular and respiratory systems are operating at race intensity. Each decision compounds with the decisions before it. These decisions are largely absent from pool racing, where the lane line, the wall, and the black T at the end of each lane handle navigation, pacing reference, and contact avoidance for the swimmer.

What the decision-making literature says about deciding while tired

The peer-reviewed evidence on cognitive performance under physical exhaustion points in a consistent direction, with caveats. Symons, Bruce, Main, and Climstein, in their 2023 systematic review published in Sports Medicine – Open, write that normal levels of fatigue experienced during standard sport competition have not been shown to impact decision making, but when athletes reach levels approaching exhaustion, decision making has been shown to decline. Reaction times measured on Stroop tasks lengthen. Errors increase. The athletes most affected are those who have accumulated stressors across both the physical and the psychological domains. The Symons review included seven studies, namely a small evidence base, and the authors note this as a limitation of the conclusions that can be drawn.

The mental fatigue literature reaches a similar conclusion from a different angle. Habay, Van Cutsem, Verschueren, and colleagues, in their 2021 systematic review published in Sports Medicine, concluded that mental fatigue induced by demanding cognitive tasks impairs sport-specific psychomotor performance across multiple sports, including those that combine perceptual processing and motor output. Marcora, Staiano, and Manning’s 2009 study in the Journal of Applied Physiology reported that mental fatigue measurably impairs subsequent physical endurance performance, namely the relationship runs both ways. Under sufficient fatigue, athletes may make slower or poorer decisions, and mental fatigue can impair subsequent endurance performance. The exact magnitude depends on the task, the duration of cognitive load, and the population studied, but the direction of effect is consistent across recent reviews.

The relevance of this literature to open water swimming is structural. Triathlon swim legs vary widely by race format, namely 750m in sprint races, 1500m in standard or Olympic-distance races, 1.9km in IRONMAN 70.3, 2km in the PTO and World Triathlon T100 series, and 3.8km in full IRONMAN. The decision burden therefore scales with distance, conditions, field density, and athlete ability rather than with one fixed time range. Across whatever duration the swim takes, the athlete is required to make navigation decisions every six to ten strokes (sighting), pacing decisions every few minutes (drafting choice, pack position, surge response), and risk-management decisions episodically (contact response, panic management, equipment failure). These decisions are being made deeper and deeper into a fatigue state. The athlete who has only ever trained in a pool has not practiced making decisions in this state, because the pool removes the decisions.

What the lane line was hiding from you, in my framework.

If open water trains decision-making, the question is which decisions specifically. I propose a five-decision schema, namely my own framework drawn from the peer-reviewed open water literature, U.S. Masters Swimming education materials, and my own race notes. The schema is not a published taxonomy, namely no peer-reviewed paper has divided open water decision-making into exactly these five categories. I find it useful for the structural argument the essay makes. Each of the five has a structural counterpart in triathlon racing.

Decision 1 · Reading the pack

In pool swimming, the swimmer’s lane is theirs. In open water, the pack is a real-time information environment. The swimmer must read the pace of nearby swimmers, the angle of the leader’s line, the pace differentials between the front of the pack and the back, the moments when the pack is fragmenting, and the moments when a stronger pack is forming on a different line. Chatard and Wilson, in their 2003 study published in Medicine & Science in Sports & Exercise with eleven trained swimmers, demonstrated that drafting behind another swimmer at four different distances (0, 50, 100, 150 cm) significantly reduced oxygen uptake, heart rate, blood lactate, rating of perceived exertion, and stroke rate, and increased stroke length, compared with the non-drafting condition. At the optimal drafting distance of 0 to 50 cm behind the lead swimmer, Chatard and Wilson reported reductions of approximately 11% in oxygen uptake, 6% in heart rate, 38% in blood lactate, 20% in rating of perceived exertion, and greater than 20% in passive drag. These are physiological effects that depend entirely on the swimmer correctly identifying which feet to follow. The decision is not a stroke decision. It is a tactical decision made under fatigue.

The triathlon analog is direct. In a non-drafting bike leg, riders must read the wind, the terrain, the pace of nearby riders to make legal pacing decisions. In a drafting-legal short-course race, the pack-reading skill transfers almost directly. In the run, the same skill applies to choosing a reference runner whose pace can pull you to the finish.

Decision 2 · Sighting

Sighting is the open water swimmer’s navigation discipline. Lift the head every six to ten strokes, find the buoy, return the head to swimming position, repeat. Every sight costs a small amount of energy and a small amount of forward momentum. Sighting too rarely sends the swimmer off course and adds distance. Sighting too often costs energy. Sighting in chop requires lifting the head higher, which costs more energy, but failing to sight in chop sends the swimmer further off course because the chop pushes the line. The decision is a continuous optimization problem under fatigue, and there is no analog in pool swimming because the lane and the T do the navigation for you.

The triathlon analog is reading the bike course at speed, namely identifying turns, hazards, pavement quality, and rider lines, while pedaling at race intensity. It is also reading the run course, namely identifying the next aid station, the next turn, the remaining distance to a competitor. Sighting trains the muscle of integrating navigation with intense physical output. Pool swimmers do not have this muscle.

Decision 3 · Managing contact

Contact in open water is constant. Feet brush feet. Hands brush hands. Bodies pass close enough to disrupt the stroke. The U.S. Masters Swimming materials note that the decision the swimmer must make when contact happens is whether to respond with aggression, with adjustment, or with relaxation, and the wrong response can escalate the situation or trigger a panic spiral. Contact response is a real-time emotional regulation problem layered on top of a physical performance problem.

The triathlon analog is the moment another rider passes you on the bike, the moment another runner surges past you on the run, or the moment something goes wrong in transition. The athlete’s emotional response in that moment, namely whether they respond with aggressive matching, with calm pace-holding, or with panic, determines what happens next in the race. The five questions the Pressure Cooker Decoder Triathlon Edition asks across the bike leg are essentially contact-response questions wearing different costumes.

Decision 4 · Judging currents

An open water race in a current is a different race than the same distance in still water. The swimmer must recognize which line through the course minimizes adverse current and maximizes following current. They must recognize when their split is slow because of fitness and when their split is slow because of conditions. They must adapt their pacing strategy to a course that is now non-uniform. Baldassarre and colleagues note that open water swimmers cannot rely on standardized pacing because the course conditions vary.

The triathlon analog is heat. A bike split at 32 degrees Celsius is not the same effort as the same split at 22 degrees Celsius. Peiffer and Abbiss, in a 2011 study cited in the Open Access Journal of Sports Medicine 2014 review of triathlon pacing factors, observed an earlier decline in power output during a 40 km cycling time trial at 32 degrees Celsius compared to cooler conditions, with subsequently lower mean power output. The heat-stress literature on pacing is essentially the current-judgment literature with the medium changed. The athlete is being asked to make pace decisions against a non-uniform environment.

Decision 5 · Controlling fear

The peer-reviewed and governing-body literature on open water swimming consistently identifies panic as a primary risk factor. The U.S. Masters Swimming materials describe the fight-or-flight response as a real physiological state that can be triggered in a race by getting a face full of water, by losing goggles, by unexpected contact, or by surf conditions outside the swimmer’s experience. The athlete who has practiced in open water before the race is not less likely to feel fear, but they are more likely to recognize the feeling early and respond with breathing regulation, position change, or temporary backstroke recovery rather than allowing the fear to escalate into a full panic episode.

The triathlon analog is the moment a power meter goes blank, a flat tire happens at km 60, the stomach rebels at km 28 of the run, or the heat exceeds the forecast by 4 degrees. Fear regulation appears to be a transferable skill across both environments, although the triggers differ. The athlete who learned it in open water has already practiced naming and managing the response. The athlete who never raced in open water is being asked to learn it for the first time during their A-race.

In my five-decision framework, open water trains five recurring decision patterns. Triathlon appears to ask versions of those patterns again across swim, bike, transition, and run.

The strongest single-paper case for open water as decision-making.

The drafting energetics literature deserves its own section because the numbers are unusually clean and the strategic implications are unusually clear. Chatard and Wilson, in their 2003 paper “Drafting Distance in Swimming” published in Medicine & Science in Sports & Exercise, conducted a controlled comparison of drafting and non-drafting positions across multiple distances behind a lead swimmer. The reductions they reported were as follows.

Delextrat and colleagues extended this work to triathlon specifically. They reported that 750m of swimming in a drafting position, compared with an isolated swim at the same pace, improved cycling efficiency in the subsequent 15-minute cycling trial by 4.8% (p<0.05) in well-trained male triathletes. Hausswirth and colleagues had earlier demonstrated that drafting during the cycling leg of a sprint triathlon produced significantly lower V̇O₂, HR, and lactate, and a subsequent run speed improvement of approximately 4% (17.8 vs 17.1 km/h) compared with cycling alone. The energetic benefit of one good drafting decision can compound across the next discipline. The athlete who drafts well in the swim may arrive at T1 with a reduced physiological cost from the swim. Whether that translates into more glycogen, lower core temperature, or any specific downstream physiological state was not directly measured in those studies and should not be claimed without further evidence.

This is the cleanest single demonstration of the thesis. Open water teaches a decision, namely “where do I position myself in the pack,” with a measurable energetic consequence. Triathlon multiplies that decision because the consequence does not stay in the swim leg. It rides forward into the bike. It runs forward into the run.

The pacing literature on heat is the open water current literature in a different medium.

Triathlon, particularly long-course triathlon, is increasingly raced in heat. The PTO and World Triathlon T100 series, the IRONMAN World Championship in Kona, and major Olympic and half-Iron events around the world frequently take place in conditions that exceed 28 degrees Celsius and high relative humidity. The peer-reviewed evidence on what heat does to athletes is consistent in two findings.

First, heat impairs pacing. The Wu, Peiffer, Brisswalter, Nosaka, and Abbiss 2014 review of triathlon-specific pacing factors identifies thermoregulation as a substantial input to pacing strategy across all triathlon distances. Peiffer and Abbiss 2011, in the same review, reported earlier declines in power output and lower mean power output during a 40 km cycling time trial at 32 degrees Celsius compared with cooler conditions. Pacing strategies that work in cool conditions can produce earlier fatigue patterns in hot conditions.

Second, the evidence on whether heat impairs the cognitive processing required to make pacing adjustments is more equivocal. Donnan, Williams, and Stanger, in their 2021 study published in Perceptual and Motor Skills, reported that complex decision-making accuracy suffered during prolonged high-intensity intermittent exercise in hot conditions, while simple-decision performance was preserved. Doohan and colleagues’ 2023 narrative review of 31 papers in the Journal of Applied Physiology concluded that core temperature changes were not sufficient predictors of cognitive performance independently, and that the evidence on heat-strain cognitive effects remains equivocal across studies. The 2023 systematic review by Donnan, Williams, and Bargh, published in Temperature, identified medium-term heat acclimation, pre-cooling, and individualized hydration as strategies with some supporting evidence, while noting that the existing evidence base on the cognitive benefits of these strategies is small and methodologically varied.

The structural finding I draw from this literature, with appropriate hedging, is that heat creates a compound problem in long-course triathlon. The body needs the athlete to make a pacing adjustment in real time, and the heat may simultaneously be degrading the athlete’s ability to recognize that the adjustment is needed. This resembles the open water swimmer’s problem in an adverse current. The current is degrading the swimmer’s pace, and the swimmer must decide whether the slow split is fitness, conditions, or both, while the swimmer’s own decision-making is itself accumulating fatigue. The athlete who has trained for current-judgment in open water has rehearsed the cognitive routine of pace-adjustment under environmental stress. Whether this transfers cleanly to triathlon is an open hypothesis, namely the hypothesis this essay is making, not a proven finding.

The same five decisions, three times, with fatigue compounding.

In my five-decision framework, open water trains five recurring decision patterns, namely reading the pack, sighting, managing contact, judging currents, and controlling fear. Triathlon appears to ask versions of those patterns again across the bike leg and again across the run leg, with the cumulative fatigue from each prior leg in the legs. The 2014 review by Wu, Peiffer, Brisswalter, Nosaka, and Abbiss in the Open Access Journal of Sports Medicine on factors influencing triathlon pacing identifies the structural challenge clearly. Triathlon pacing is influenced by fuel availability, thermoregulation, prior experience, knowledge of exercise duration, physical fitness, cognitive capacity, mood, peripheral feedback, and central regulation. The athlete is making integrative decisions across multiple input streams while three different physiological systems are fatiguing simultaneously.

The decisions that triathlon adds to the open water decision set are themselves significant. They include the transition decisions, namely the T1 sequence (wetsuit off, helmet on, shoes on, mount the bike) under cardiovascular load and the T2 sequence (off the bike, shoes changed, hat on, run) under cumulative fatigue. They include the bike-leg decisions, namely pace selection against power, terrain, and wind, response to other riders, nutrition timing, mechanical-failure response. They include the run-leg decisions, namely pace selection against accumulated fatigue, response to cramps and stomach issues, response to heat, response to rivals seen on the course.

Each of these decision categories has the same internal structure as the open water decision categories. Each requires the athlete to integrate environmental information with their own fatigue state and produce a response that is not panicked, not overconfident, and not based on outdated assumptions about the race. The Pressure Cooker Decoder Triathlon Edition, the companion tool to this essay, is a 15-question instrument designed to surface the athlete’s actual response pattern across these decision categories, namely the persona that emerges when the plan dies and only decisions remain.

The argument I want to make explicitly is this. The triathlete who has raced open water is not just a triathlete who has done extra swim training. I propose that the triathlete who has raced open water has rehearsed components of the decision-making system that the bike and run legs of triathlon will require. For shorter triathlon distances, the swim leg is the first portion of the race during which the athlete is operating a decision-making muscle that has to last the rest of the day. A pool athlete entering triathlon for the first time may need to learn elements of this decision-making system from scratch under race conditions. An open water athlete entering triathlon may have already rehearsed parts of the system. This is a hypothesis, namely a position the convergent literature supports but does not prove. The direct comparison, namely whether open water-trained athletes adapt to triathlon faster than pool-only athletes of similar fitness, has not, to my knowledge, been tested in a controlled study. I would welcome that study.

A pool athlete moving to triathlon learns three sports. An open water athlete moving to triathlon learns two sports and applies an existing decision system across all three.

What I actually learned in Cyprus and Kazakhstan.

The thesis above is supported by the peer-reviewed literature. The lived case is my own. I race open water, namely I won the 10 km Oceanman Aktau 2025 race overall and placed first in the Junior category at Oceanman Ayia Napa 2025 over 10 km, and I am now training for sprint and Olympic-distance triathlon. What I have noticed across my own racing, and what the coaches I work with confirm, is that the decision-making the open water race forced me to develop is the part of triathlon I am finding least difficult to add to my existing fitness.

The bike leg in a sprint triathlon, on a course I have never seen before, requires the same buoy-equivalent decisions I made in chop, namely where is the next turn, how is my pace lining up against my plan, what is the wind doing to my line, who is around me, and what does my body actually feel like under this load. The transition decisions, namely the T1 sequence specifically, have been the hardest to learn for me, because nothing in open water specifically rehearses the wet-to-dry equipment changeover under cardiovascular load. That is honest. The open water athlete still has to learn transitions. But the integration of pace, position, navigation, and emotional regulation across three disciplines was already trained.

The run leg has been the most surprising. The decision routine of “what does my body actually feel like, what should I adjust, what should I commit to, how do I respond to that runner ahead of me” is structurally identical to the routine I run in the back half of a 10 km open water race when the chop is bad, the cramps are starting, and the lead pack is 200 meters ahead. The body parts being recruited are different. The decision routine is the same. The open water race trained the routine first. The triathlon is now applying it.

I want to be careful with this section. It is one athlete’s observation and it is not peer-reviewed evidence. I include it because the thesis above is testable on a population of athletes who have moved from pool swimming to triathlon versus a population of athletes who have moved from open water swimming to triathlon, and to my knowledge that comparison has not been done formally. The hypothesis the literature supports, and that my lived experience supports, is that the second population should adapt to triathlon faster, with fewer pacing errors and fewer panic responses, than the first.

The Lessons from the Water discipline: educational, reflective, not diagnostic.

An essay can argue that decision-making under uncertainty is the foundation of endurance racing. An essay cannot show the reader their own decision-making profile. That is what the companion tools attempt, namely to give the reader a structured way to think about how they themselves might respond to race-pressure scenarios. The discipline I take from the athlete-and-coach craft, namely the practice of giving athletes a vocabulary for what they do under pressure, motivates pairing this essay with two interactive tools. This essay sits in the Lessons from the Water series on this site, namely the body of work I am developing on what open water swimming and triathlon teach about racing, decision-making, and training the brain alongside the engine.

What the tools are. They are educational, reflective, self-report scenarios that surface a likely response pattern under simulated race pressure. The Open Water Edition asks twelve scenarios across the swim. The Triathlon Edition asks fifteen scenarios across swim, T1, bike, T2, run, and finish-line confession. Each tool produces a primary persona, a secondary persona, three performance meters, a fracture point with severity tier, and earned badges. The output is intended as a prompt for reflection, training-partner conversation, coaching discussion, or race-plan review.

What the tools are not. They are not validated psychometric instruments. They are not diagnostic tools. They are not performance predictors. They are not coaching prescriptions. They have not been tested for psychometric reliability, predictive validity, or population norms. The personas are author-constructed archetypes drawn from triathlon coaching literature and my own racing experience, namely they are not derived from a peer-reviewed taxonomy of athlete decision-making. The fracture-point and severity-tier outputs are pattern matches against the user’s own answer choices, namely they tell the user what their answer pattern reveals, not what their actual race outcome will be. The result is a conversation starter, not a verdict.

The honest framing is this. The literature this essay reviews supports the position that decision-making under fatigue is a real and trainable component of endurance performance. The athlete who can name their likely response pattern can talk about it with their coach, monitor it in training, and rehearse alternative responses. The tools exist to help athletes name the pattern. They do not replace coaching. They do not replace race experience. They do not replace the validated sport-psychology assessments that exist for clinical or applied use. They are an entry point.

What this essay does not claim, and where the evidence runs out.

An honest piece of writing names its own limits. This essay has several worth stating clearly. First, the central proposition is a hypothesis, not a finding. The claim that open water-trained triathletes adapt to triathlon faster than pool-only athletes of similar fitness is, as far as I have been able to determine, not yet tested in a controlled study. The convergent literature on drafting, fatigue, and decision-making is consistent with the proposition. It does not prove it. Second, the five-decision schema is my own framework, namely it is not a published taxonomy and other authors might divide open water decision-making differently. Third, several of the cited studies have small sample sizes, namely Chatard & Wilson 2003 (n=11), Delextrat 2003 (n=8), Hausswirth 1999 (n=8), Donnan 2021 (n=12). Effects observed in small samples of trained athletes do not necessarily generalize to all populations or all distances. Fourth, the heat-and-cognition evidence is equivocal, namely the 2023 narrative review by Doohan and colleagues explicitly concluded that core temperature changes alone are not sufficient predictors of cognitive performance. I cite the heat literature because it is relevant to the structural argument, not because it settles the question of how heat affects athlete decision-making. Fifth, my own race notes are exactly that, namely one athlete’s observations, presented as illustrative and not as evidence. The peer-reviewed literature carries the argumentative weight. The race notes carry the voice.

The thesis again, in one sentence.

Open water swimming is endurance plus decision-making under uncertainty, and I argue that combination is a strong foundation for triathlon. The pool athlete entering triathlon may need to learn elements of three sports at once. The open water athlete entering triathlon may have already rehearsed parts of the integrative decision-making system that triathlon requires. The peer-reviewed literature on drafting energetics, fatigue effects on cognition, heat-stress effects on pacing, and triathlon pacing factors is consistent with this position. It does not prove it. The direct comparison has not, to my knowledge, been tested. I would welcome the test.

The companion tools are reflective instruments, not validated assessments. The argument is that you should use them to surface a likely response pattern, take that pattern to your coach or training partner, and rehearse the alternative responses you find missing in your own race brain. That is the discipline behind Lessons from the Water, namely the practice of naming what you do under pressure so you can train it. Show your work. Acknowledge what you do not know. Read your own race honestly. Train the system, not just the engine.

Calculate · Commit · Continue

Kerim Demirkol competes in open water swimming and triathlon. He won the 10 km Oceanman Aktau 2025 race overall and placed first in the Junior category at Oceanman Ayia Napa 2025 over 10 km. He is a Certified Fitness Trainer (EQF Level 4, EREPS / EuropeActive), a FIDE Arena International Chess Master, and a Borlaug Scholar through the World Food Prize Foundation and the Wageningen Youth Institute. He is the creator of the KimDem music project. More at kerimdemirkol.com.

Open water teaches the muscle. Triathlon multiplies it. Train the system, not just the engine.

An independent essay by Kerim Demirkol, with no brand sponsorship and no commercial relationship to any organization named here. Companion tools: Open Water Edition · Triathlon Edition.