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Cold Water Survival

The first few seconds can be the most dangerous. By Darrell Nicholson - Updated:January 25, 2021

When we read about a sailor lost overboard in a storm, we think about PFDs and personal locator beacons, and accept the sea is unforgiving. When we read of novice boaters drowning in a local lake, we’re sad, but say that will not happen to us because we wear PFDs. But when we read of a PFD-equipped sailor falling overboard and dying within minutes, it’s a real eye-opener.

Spring sailing in temperate climates still carries the risk of cold water shock. With the water temperature in the low 50s, true hypothermia sets in at about 30 minutes. Swimming can be difficult after about 20 minutes. However, 50 degrees is well below the accepted threshold of shock. Most likely, when the icy water slams into a person’s face it causes an involuntary gasp. It’s hard to recover from inhaling water, even for a strong swimmer.

Originally known as sudden disappearance syndrome, cold water shock has been known since the 1970s. Different from true hypothermia, which results from the body core temperature dropping over a period of 20 minutes to hours, cold water shock is immediate. Being cast headfirst into icy water is one of most severe shocks a human can face, with deadly effects. It is estimated that 20 percent of victims die within 2 minutes.

Physical effects

The instantaneous reflex is a violent gasp, totally unlike the one scary movies strive to cause. This results in a massive in rush of air, which can be fatal if you are underwater. Unlike the controlled plunges of the local polar bear club, where participants walk in via a beach and are attended by rescue swimmers in dry suits, MOB sailors plunge in head first, the result of tripping over the lifeline. Even with an automatic vest, your head will plunge 6 feet underwater before popping to the surface. If the first blast of inhaled water doesn’t drown you, you’ll arrive on the surface gasping and unable to swim and swallowing more. Drowning will typically occur in less than a minute. The initial gasp is followed by several minutes of hyperventilation, making any physical effort nearly impossible. Consequences include the inability to hold your breath or think clearly.

Instantaneous and massive increases in heart rate and blood pressure can cause heart failure in otherwise healthy individuals. Clear thought is impossible. Panic is likely, only serving to increase problems with breathing control and heart rate.

These reactions may appear to an observer as nothing more than panic. Flailing, spastic breathing, muddled thinking, and a racing heart fit the pattern. But victims include experienced sailors and strong swimmers who are not at all prone to panic. If you fall overboard in warm water and reasonable weather, your first concern might be embarrassment over screwing up the race, and later whether the boat would be back in the next half or hour so. It wouldn’t have felt life threatening.

If you survive the first critical seconds, then come the more traditional challenges of cold water exposure. Cold incapacitation and swimming failure begins in 5-20 minutes, the result of failed muscle control. In the absence of a PFD, drowning follows. Death from true hypothermia (cold core) takes considerably longer, at least 30 minutes in very cold water up to a few hours in cool water.

How do you keep this from happening to you? First, don’t fall in. The first line of defense is careful movement and the use of harness and tether systems as described in PS October 2018. If sailing a smaller boat, prone to capsize or swamping, dress for full water immersion. In cool water either a thin wetsuit or dry suit is effective. Once the water temperature drops below about 50F, only a dry suit is suitable. (See PS November 2018 and March 2009.)

If performing high risk activities on larger boats (hiking out, working on the bow, or leaning outboard) a dry suit is the smart option. It is our favorite foul weather gear for stormy conditions in cool weather; more agile than heavy foul weather gear and nary a drop of water will go down your neck. Small wonder is increased in popularity with offshore racers and sailors.

Unfortunately, once the air temperature gets above about 55F, dry suits get steamy, tempting the wearer to open the zipper and defeating the whole purpose. As the water temperature rises into the 50s, we like paddling jackets and dinghy smocks, with snug fitting wrist, neck, and waist seals. Water will sneak in pretty quickly, but shock is reduced and the seals reduce the exchange of cold water. The wearer is also more mobile than in conventional foul weather gear.

Soft shells may also have possibilities. Once our tester found himself in 35F water, with ice around the edges. He was dressed not in foul weather gear or dry suit, but in Wind Blocker fleece tops and bottoms. The saving factors were that the wrist, waist, ankle, and neck closures were all tightly secured; not all soft shells have effective closures. Although very cold, it was more survivable than ordinary foul weather gear.


The last 12 months have been hard on ocean racers. It is more than coincidence cool or cold water was a common factor. In the UK, coldwater shock is considered to be the root cause of most drowning, including non-boating accidents.

We like certain features of manual inflating PFDs; they don’t go off inadvertently and climbing back aboard is easier. But cold water is different. Because of the high probability the wearer will be incapable of action for a minute or more, auto-inflation is the way to go.

We would like to see the makers of foul weather gear take a long hard look at what can be done to improve cold water shock resistance. Conventional jackets and soft shells could be fitted with effective internal neck seals. Wrist and waist seals could be upgraded.

We would like to see race committees post cold water warnings. It is common to require PFDs be worn above a certain wind speed. The race committee should at least recommend that protective gear such as a wet suit or drysuit be worn if the water temperature is below about 55 F. Our level of caution around the rail varies with the risk we perceive, and that level of caution goes way up when the water temperatures go down.

Most importantly, sailors need understand what being thrown face first into cold water feels like and how their body will respond to it. A diehard for traditional foul weather gear? Don’t fall off the boat in cold water, and don’t expect to survive more than a few minutes if you do. Its tough out there.

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