The single most important step is to get the person out of the water and onto a dry surface before you attach or use an automated external defibrillator (AED). Water conducts electricity across the skin and can short the pads, so neither you nor the device can work safely while the victim is still wet or in the water. Once on land, dry the chest, then follow the AED's prompts. Everything else—pad placement, shocking, CPR—depends on that first extraction and drying step.
Drowning kills through hypoxia, not through a primary heart attack. That single fact reshapes every AED decision, from where you kneel to when you shock. This explainer walks through the mechanism, the numbers, the edge cases that trip up trained responders, and the exact sequence to run. It is written for the lay rescuer and the professional who wants the physiology behind the checklist.
Why water and electricity change the AED sequence
An AED works by pushing a controlled current between two pads to depolarize the heart muscle all at once. Current follows the path of least resistance. A wet chest, a puddle, or a body still lying in water gives that current an escape route across the skin surface rather than through the heart. Surface water can bridge the two pads and cause arcing or a shock that never reaches the myocardium.
Wet skin also lowers transthoracic impedance, the electrical resistance the device must overcome. Defibrillators compensate for impedance, but a layer of water confounds that compensation and can degrade pad adhesion. Pads that float or peel deliver less energy to the heart. The device may read "check pads" or fail to analyze the rhythm accurately.
There is a second, independent hazard. Water on the ground around the rescuer creates a shock path if the rescuer is kneeling in it while the device discharges. Modern AEDs are designed to mitigate this, but the safe assumption is dry victim, dry pads, dry rescuer. Movement of a wet body also generates artifact that confuses the rhythm analysis algorithm. The machine cannot tell ventricular fibrillation from a noisy wet connection.
Plain language: the AED needs a clean electrical window through a dry chest to see and fix a lethal rhythm.
What the numbers say about drowning and shockable rhythms
Drowning is a leading cause of unintentional injury death worldwide, and the ventricular fibrillation window in drowning is narrow. Cardiac arrest from drowning usually begins as asphyxia, producing a slow pulseless electrical activity or asystole rather than the chaotic electrical storm of ventricular fibrillation. That matters because AEDs only shock two rhythms: ventricular fibrillation and pulseless ventricular tachycardia.
Because hypoxia precedes cardiac arrest, the proportion of drowning victims found in a shockable rhythm is low and falls fast with time. Responders who arrive within a few minutes of submersion are more likely to encounter a shockable rhythm than those arriving after ten minutes of untreated arrest. The practical consequence: high-quality CPR and rescue breaths reopen the oxygen pipeline, and the AED is a supplement, not the star.
Rescue breathing deserves emphasis here. In drowning, the primary problem is oxygen starvation, so ventilations matter more than in a typical cardiac arrest. Current guidance from the American Heart Association emphasizes rescue breaths alongside compressions for drowning victims. An AED that shocks a hypoxic heart without oxygen delivery often produces a transient rhythm that immediately decays.
The AED's own timing matters too. Analysis typically takes 5 to 15 seconds, and a shock is delivered within seconds of the prompt. Chest compressions should resume immediately after a shock. Every second of hands-off time lowers the chance of return of spontaneous circulation.
Edge cases that change the plan
Cold-water immersion is the classic counterintuitive case. A person submerged in cold water can survive prolonged arrest because hypothermia lowers cerebral oxygen demand and can preserve brain tissue far longer than warm-water drowning. Rescuers should not withhold an AED or CPR based on a presumed poor prognosis. Continue resuscitation and use the AED as directed; the device's rhythm analysis remains valid, though severely cold myocardium may be refractory to shocks until rewarming.
Hypothermia also blunts the electrical response. A heart below roughly 28 to 30 degrees Celsius may not respond to defibrillation at all. Professional caveat: in profound hypothermia, some protocols advise delaying shocks until rewarming, but lay rescuers should follow the AED's prompts and continue CPR. Do not withhold a shock the device advises.
Another edge case is the victim who was submerged in salt water versus fresh water. Both are dangerous and both require the same extraction-and-drying step, but seawater is more conductive and leaves a residue that can reduce pad contact. Wipe and dry the chest thoroughly either way.
Vomiting is common in drowning resuscitation because swallowed water and gastric contents are expelled. Emesis on the chest ruins pad adhesion and creates a shock hazard. Clear and dry the chest, then reapply fresh pads. Do not shock across a wet, soiled chest.
Finally, consider the victim with a pacemaker or implanted defibrillator. Place pads at least 8 inches (about 20 cm) from the device generator, and never directly over it. The device can interfere with rhythm analysis, but it is not a reason to skip the AED.
Do not use an AED on a person still in water or lying in a puddle. Do not apply pads to a wet, vomit-covered, or snow-covered chest without drying and clearing it. Do not let anyone touch the victim during analysis or shock delivery. Do not place pads directly over an implanted pacemaker or defibrillator generator. Do not delay CPR to fetch an AED if one is more than a short sprint away; start compressions and send someone else. Do not assume a drowning victim is "too far gone" after cold-water immersion; prolonged resuscitation can succeed.
Misconceptions that cost seconds
The most damaging myth is that you should "get the water out" before starting resuscitation. Attempts to drain water from the lungs by pressing the abdomen or lifting the legs waste time, cause vomiting, and do not improve oxygenation. The lungs absorb most aspirated water quickly; what remains is not the barrier to ventilation that rescuers imagine. Skip the drainage and go straight to extraction, drying, and CPR.
A second myth is that an AED cannot be used on a wet victim at all. The device can be used, but only after the victim is moved to a dry surface and the chest is dried. The rule is dry surface, dry chest, dry hands, not "no AED near water."
A third misconception is that the AED replaces rescue breaths in drowning. It does not. Because the arrest is hypoxic, ventilations are integral. Compression-only CPR is better than nothing, but for drowning the standard is compressions plus rescue breaths.
A fourth is that a shock "restarts" the heart. A shock actually stuns the heart momentarily to stop a chaotic rhythm and let the natural pacemaker resume. If the heart is in asystole, a shock does nothing and may harm. That is why the AED analyzes before advising.
The practical sequence, step by step
Extraction comes first. Remove the person from the water and lay them flat on a firm, dry surface. If the surface is wet, move them or create a dry barrier. This is the step that makes every later step safe.
Check responsiveness and breathing while you send someone for the AED and call emergency services. If the person is unresponsive and not breathing normally, begin CPR immediately with compressions and rescue breaths. Do not wait for the AED to start compressions.
Dry the chest vigorously with a towel or cloth. Pay attention to the area between the pads, not just the pad sites. If the chest is hairy, the AED kit usually includes a razor; shave the pad sites if hair prevents adhesion. If the chest is soiled, wipe it clean and dry it again.
Turn on the AED and follow its voice prompts exactly. Expose the chest fully, apply pads to the bare, dry skin in the positions shown on the pad diagram, and plug in the connector if required. Make sure no one, including you, is touching the victim while the device analyzes. Announce "clear" before any shock and visually confirm everyone is off the patient.
Resume compressions immediately after the shock or after a "no shock advised" message. Continue the cycle of 30 compressions to 2 breaths for adults, or the ratio your training specifies, until EMS arrives or the person shows signs of life.
Timing the response: what each minute buys you
| Time since submersion | Typical rhythm | AED role | Priority action |
|---|---|---|---|
| 0–2 minutes | Often still perfusing or early arrest | Prepare, do not delay CPR | Rescue breaths and compressions |
| 2–5 minutes | Rising chance of VF | Attach and analyze promptly | CPR plus early AED |
| 5–10 minutes | Mostly PEA or asystole | Shock only if advised | High-quality CPR, ventilations |
| 10–20 minutes | Asystole common | AED confirms non-shockable | Sustained CPR, consider hypothermia |
| Over 20 minutes, warm water | Asystole | Low yield but not zero | Continue until EMS or exhaustion |
| Over 20 minutes, cold water | Variable | Continue as directed | Prolonged resuscitation may succeed |
These ranges are approximations drawn from resuscitation physiology, not fixed cutoffs. They illustrate a trend: the earlier the rescue, the more the AED can do.
Where the evidence and the device stop
An AED is a decision-support tool, not a diagnostician. It cannot tell you why the person arrested, and it cannot reverse hypoxia. It analyzes a single electrical signal and advises a shock or no shock. Everything upstream, from extraction to ventilation, determines whether that advice can save a life.
There are also device limits worth knowing. AEDs are not approved for use on children under about 1 year without pediatric pads or a pediatric mode, and even then, follow the device labeling. They are not for traumatic arrest with obvious signs of death, and they are not a substitute for calling emergency services. Battery and pad expiration dates matter; check them during routine inspections.
The honest limitation is this: in drowning, the AED is often a supporting actor. The lead roles belong to rapid extraction, immediate ventilations, and uninterrupted compressions. Rescuers who understand that hierarchy use the AED correctly and at the right moment.
This article is general educational information about emergency response, not a diagnosis, treatment plan, or substitute for certified training. It does not promise any outcome. For hands-on skill, take a course from a recognized provider such as the American Red Cross or American Heart Association, and in any emergency call your local emergency number immediately.