A polar plunge is a deliberate, brief dip into near-freezing water, typically done outdoors during winter months. Some people do it solo as a cold-water practice, but the term most often refers to organized events where crowds of people charge into icy lakes, rivers, or ocean water together, often in costumes and usually to raise money for charity. What started as a Scandinavian tradition of cold-water dipping has turned into a global phenomenon, with thousands of events held each winter.
How Polar Plunge Events Work
Most organized polar plunges follow a simple format. Participants register, raise a fundraising minimum, then wade or run into frigid water as a group. The actual time in the water is short, often just seconds to a couple of minutes. Organizers set up heated tents or warming areas nearby so plungers can dry off and warm up immediately after.
The biggest polar plunge series in the United States benefits Special Olympics programs. In Virginia alone, these events have raised more than $24.5 million since 1993. A single recent event in Virginia Beach drew 3,000 participants and raised $1.7 million. New Year’s Day plunges are another major tradition, with “Polar Bear Plunges” held in cities around the world to mark the start of the year.
What Happens to Your Body in Cold Water
The moment you hit cold water, your body launches a powerful involuntary reaction called the cold shock response. Your skin temperature drops rapidly, triggering a gasp reflex followed by fast, uncontrollable breathing. At the same time, your fight-or-flight system floods your bloodstream with adrenaline and stress hormones. Your heart rate and blood pressure spike. Blood vessels near your skin constrict to conserve heat, pushing extra blood toward your chest and core organs, which puts added strain on the heart.
This entire cascade happens within the first 30 to 90 seconds and is the most dangerous window of a polar plunge. The gasp reflex alone is a drowning risk if your head goes underwater. After that initial shock passes, your body begins to stabilize, though you’ll continue losing heat the longer you stay submerged.
The Mood and Energy Boost
The rush people describe after a polar plunge isn’t just adrenaline or bravado. Cold water immersion triggers a massive release of brain chemicals tied to alertness and mood. Research has measured a 530% increase in noradrenaline, which sharpens focus and arousal, and a 250% increase in dopamine, the chemical responsible for feelings of pleasure and satisfaction. That dopamine surge is comparable to what certain medications produce, and it can last for hours after you leave the water.
This is the main reason many people become repeat plungers. The combination of overcoming a physical challenge, the social energy of a group event, and a genuine neurochemical high creates an experience that people describe as euphoric. It also helps explain the growing popularity of regular cold-water practices like ice baths and cold showers.
Immune System Effects
Regular cold-water swimming appears to prime the immune system over time. A study of winter swimmers found that a single session increased total white blood cell counts by about 41%, with notable jumps in the specific immune cells that fight infection: a 43% increase in one type of first-responder cell, a 58% increase in lymphocytes (which target viruses and bacteria), and a 28% increase in monocytes.
More interesting is what happens with repeated exposure. Experienced winter swimmers showed higher baseline levels of key immune cells even at rest compared to newcomers. Their immune cells also responded more effectively when challenged, suggesting the body gradually learns to mount a stronger defense. This doesn’t mean a single polar plunge will prevent a cold, but habitual cold-water exposure does appear to shift immune readiness over weeks and months.
Who Should Skip It
The cardiovascular stress of cold water immersion is real, and for certain people, it’s genuinely dangerous. The surge of adrenaline can disrupt the heart’s steady rhythm, which is usually harmless in a healthy heart but potentially life-threatening for anyone with an existing heart condition. People with atrial fibrillation or other heart rhythm disorders should avoid cold plunges entirely. The same applies to anyone with a history of cardiovascular disease, circulation problems like peripheral artery disease, or Raynaud’s syndrome, where cold triggers extreme narrowing of blood vessels in the fingers and toes.
The confused signaling between the cold shock response (which speeds the heart) and the body’s diving reflex (which slows it) can produce irregular heart rhythms even in people who didn’t know they were at risk. This is why sudden cardiac events, though rare at organized plunges, do occasionally happen.
How to Prepare
Preparation makes the difference between an exhilarating experience and a miserable one. Wear shoes into the water. Most organized events require them, and for good reason: your feet will go numb quickly on frozen ground, and lake or river bottoms can be rocky. Sturdy sandals with straps, water shoes, or old sneakers all work. Skip flip-flops.
Bring a towel and a full change of dry clothes, including warm layers. Have them staged as close to the water as possible so you can start warming up within seconds of getting out. Most organized events provide a heated tent or indoor space, but you’ll still need your own dry gear. A wool or fleece hat is worth packing since you lose significant heat through your head.
If you’ve never done cold-water immersion before, a few cold showers in the days leading up to the event can help your body practice the shock response in a controlled setting. The goal isn’t to eliminate the gasp reflex but to make it less overwhelming so you can control your breathing when you hit the water.
Warming Up Safely After
How you rewarm matters as much as how you go in. The key principle is warming slowly and starting with your core. Strip off wet clothes immediately and towel dry. Wrap up in dry blankets or layers, focusing on your torso and abdomen first rather than your hands and feet. This sounds counterintuitive since your extremities will feel the coldest, but warming the core first prevents cold blood in your limbs from rushing back to your heart too quickly, which can trigger dangerous heart rhythm problems.
Hot water bottles or chemical hand warmers can help, but wrap them in a towel before placing them against skin. Do not jump into a hot shower or hot tub right after. Rapid external warming can cause blood pressure to drop suddenly and increases the risk of cardiac arrhythmia. Warm drinks, dry layers, and a heated room are the safest approach. Give your body 20 to 30 minutes to come back to normal gradually.