When tragedy strikes at one of the most grueling sporting competitions on Earth, it would be easy to assume that a lack of preparation was to blame.

Unfortunately, the unseen dangers remain even for the most well-trained athletes.

Mara Flávia, a 38-year-old Brazilian influencer and triathlete, drowned during the open-water swimming endurance portion of the Texas Triathlon in Lake Woodlands on Saturday.

The Montgomery County Sheriff’s Office confirmed that the victim “drowned while participating in the swim portion of the event,” according to a statement, as its Major Crimes continues their investigation “per normal protocols.”

At the time of reporting, the exact cause of Flávia’s death remains unclear. But even under the best circumstances with the most trained athletes, risks abound

“While most people focus on the physical exhaustion of triathlons, the most overlooked risks are often environmental and physiological,” Tyler McDonald from the National Academy of Sports Medicine (NASM), whose work focuses on athletes and performance, told The Post.

“Even the strongest swimmers can be sidelined by the chaos of open water.”

Statistically, the swim portion is where the majority of triathlon fatalities occur because it’s the only segment where a minor medical event can lead to drowning, McDonald explained.

“Unlike the bike or run, where you can simply stop and sit down, the water is an unforgiving environment where you must maintain buoyancy while dealing with a crisis,” he said, noting that a panic attack, a brief heart arrhythmia or even a cramp can be fatal.

Plus, an open-swim competition comes with a lot of outside factors that are out of the athletes’ control. At NASM, they refer to the “washing machine effect.” During the mass start of the swim section, triathletes are faced with a whirl of arms and legs all around them — and getting kicked or pushed underwater can trigger an instant panic response, McDonald explained. Once fight or flight kicks in, rhythmic breathing “goes out the window, and even a pro can start to struggle.”

Open water also lacks the “black line” of a pool, which can lead to visibility and orientation issues. Losing sight of the shore or buoys due to glare or choppy water can result in spatial disorientation, ultimately leading to inefficient swimming and rapid exhaustion.

But the most overlooked risk participants face in the swim portion of a triathlon is the temperature of the water. According to McDonald, cold water shock can cause an involuntary gasp reflex, leading to water inhalation before the swimmer even starts their first stroke.

To help combat this, he advised warming up in the water prior to the race if possible, and “never start a race cold.” Getting a 5- to 10-minute acclimation in the water before swimming can help mitigate the cold-water shock response.

He added that the “powering through” mentality, a misconception that belies a triathletes readieness or safety, encourages competitors to push through the pain in training, ignoring symptoms like chest tightness, extreme lightheadedness or sudden tingling — all of which shold be considered red flags.

Many people in the r/IronmanTriathlon sub-Reddit page echoed this sentiment, with one person saying the tragedy that occurred in Texas “furthers my hate for the ‘lol I just need to survive the swim’ mentality.”

“I’ve been around long enough to have known about (or race at) multiple races that have had swim deaths. It’s usually nothing to do with the athlete’s swim competence, and more to do with multiple contributing factors that create a ‘perfect storm’ with a tragic outcome,” another user wrote.

“Hearing about what happened on the swim made me reflect on how much I’ve probably underestimated that part of the race and the real risks involved,” someone who competed in the same race shared.

With all these potential risks, McDonald said every athlete should be able to master the “safety stroke,” flipping onto their back and performing a relaxed breaststroke or backstroke to lower their heart rate.

“In a triathlon, there is a fine line between mental toughness and ignoring a medical emergency,” McDonald told The Post.

It’s not just the swimming portion of a triathlon that athletes need to be careful with. When it comes to the bike portion, the most overlooked risk is cognitive fatigue, McDonald said. As blood sugar drops, reaction time slows, which makes high-speed technical descents much more dangerous than the physical exertion itself.

With the run, the risk is often cardiac drift, where heart rate rises steadily despite maintaining a constant pace due to heat stress and dehydration. This can put an unexpected strain on the cardiovascular system late in the day and pose a potential risk.

In general, exertional hyponatremia, potentially fatal condition where blood sodium levels drop dangerously low from over-drinking plain water, can affect even the best-trained athletes, McDonald said.

Using the “sweat rate test” during training can help athletes determine how much fluid and electrolytes their body will need on race day, and figuring this out in advance can prevent any day-of guessing.

Many athletes may also have undiagnosed underlying heart conditions such as hypertrophic cardiomyopathy that can be triggered by the “perfect storm of race-day adrenaline, cold water and max-effort exertion.”

Before starting a high-intensity program, McDonald recommends getting a cardiac screening with a simple EKG or stress test can identify any hidden risks.

No matter how much one trains for or participates in a triathlon, there are always risks to the big race.

“Preparation doesn’t make you bulletproof,” McDonald urged, adding that training alone is not always going to protect an athlete.

“Training usually happens in controlled environments, lanes in a pool or familiar roads. This training builds aerobic capacity, but it doesn’t always build resilience to chaos,” he explained. “A highly trained athlete might have the engine to finish, but if they haven’t practiced sighting in choppy water or drafting in a crowd, their body’s stress response can override their physical conditioning.”

McDonald’s single most important advice to athletes preparing for a triathlon is to train for the environment, not just the distance. For example, if your race is going to be in the ocean, practice in the ocean. If it’s a hilly course for the bike, don’t only practice cycling on flat roads or courses.

“Familiarity with the specific stresses of the race-day environment is what keeps your mind and your body calm in the chaos, and staying calm is what keeps you safe,” he said.