In evaluating more than 1,000 fatal drownings, I have discovered that there is considerable confusion about drowning and its process, even among aquatics professionals. My objective here is to identify and correct some misunderstandings about what really happens when an individual drowns, from a physiological and behavioral perspective.

The misunderstandings and confusion begin with the definition of drowning. Historically there have been several accepted definitions. The most popular one states that drowning is death secondly to asphyxia while immersed in a liquid. This equates drowning to death.

At the 2002 World Congress of Drowning, a consensus was reached on a new definition: “Drowning is a process resulting in primary respiratory impairment from submersion in a liquid medium.” By this definition, death is no longer implied. However, most people, including some aquatics professionals, continue to believe that drowning equates with death.

While there are no accurate statistics about how many people suffer a submergence event and survive, an educated guess is more than 99%.

The CDC estimates that approximately 4,000 people fatally drown every year. However, evidence suggests that this is number is seriously underestimated for four reasons:

• When an individual falls from a boat and fatally drowns, the drowning is classified as a boating fatality, not a drowning.

• Hundreds of migrants drown along the Mexico/U.S. border while crossing the Rio Grande, All American Canal and Florida Straits. They seldom are included in drowning statistics.

• When someone dies 24 hours or later after the event, it is coded as a secondary drowning, never a drowning.

• Medical examiners often code drowning incorrectly, characterizing them as cardiac arrest or other episodes and ailments.

While the definition of drowning was updated, there are many other ways of defining drowning — some that contribute to a better understanding about the process.

Active vs. passive

While the new definition of drowning rejects these two descriptions, they are useful in understanding drowning before and just after a victim submerges underwater.

An “active” drowning involves a conscious victim, usually a non swimmer or poor swimmer, who can no longer keep their head above water. Usually, an active drowning victim progresses from a stage of distress to one of drowning. The time of this progression varies significantly, from less than a minute to several minutes. When victims are caught in a rip current, the period of distress can even be considerably longer.

The behavior of an active-drowning victim usually begins with struggling. Movies and TV often portray this by showing victims who violently panic and yell for help. In reality, this never happens. Usually the victim begins struggling without making much noise. Among toddlers and babies, drowning is often silent. This is why responsible adult supervision is so important.

In real life, this struggling involves arms moving rapidly up and down and legs back and forth — a far cry from portrayals. Lifeguards sometimes call this behavior “climbing the ladder.” As they struggle, a victim begins to hyperventilate as the head goes lower and lower. Sometimes a victim will attempt to roll over on their back, but usually this is futile. Finally, the victim submerges.

I have interviewed more than a dozen victims who almost fatally drowned. Several were biologically dead and subsequently resuscitated. In addition, I have evaluated several fatal drownings captured on video. I’ve learned that this is what usually happens: Following the surface struggle described above, the victim submerges and holds their breath, resisting the urge to breathe. This may last a minute. In discussing this stage, victims reported unbearable pain, with a feeling that their head is about to explode.

A high concentration of carbon dioxide combined with a low concentration of oxygen in the blood triggers the need to take a breath underwater. In the first breath, copious amounts of water are inhaled. As water reaches the airway, the larynx usually closes, preventing water from reaching the lungs. The victim soon loses consciousness. The spasm relaxes, allowing water to enter the lungs and disrupt the surfactant, causing the alveoli to collapse and prevent life-giving oxygen from being diffused into tissues and from reaching the vital organs.

While breathing has ceased, the heart usually continues to beat, but at an accelerated rate. Before stopping, it may progress to a stage of fibrillation. Once breathing and the heart stops, the victims is biologically dead.

The term passive drowning is seldom used but still helps explain how several causes can quickly render a victim unconscious without the described struggling. An inventory of passive drowning causes include:

• Cardiac event

• Electrocution

• Shallow water blackout

• Seizure

• Drug and alcohol

• Trauma

Drugs and alcohol are involved is about 50% of all fatal drownings. In some aquatic environments, such as hot tubs, and among young men and late teens, the percent is significantly greater than 50%.

Cold water drowning

Cold water drowning occurs when the water temperature is less than 68 degrees Fahrenheit (20 degrees Celsius). At this temperature threshold, the body begins to experience hypothermia, as water dissipates body heat faster than air.

The mammalian reflex is a physiological response to drowning in cold water and is most pronounced among children. This reflex is responsible for shunting blood from the extremities and directing it to the vital organs, thus prolonging the time between biological death and clinical death, and the time of irreparable brain damage. Although rare, there are several cases where children have fallen through ice into water slightly above freezing for more than 20 minutes with no neurological impairment.

Dry drowning vs. wet water drowning

In theory, a dry drowning results when water comes in contact with the esophagus, causing it to spasm and close. This prevents water from entering the lungs. There are several opinions that about 20 percent of fatal drowning are dry. However, one study following a number of post mortem examinations refuted this percentage, claiming that dry drownings are exceedingly rare.