Cold Water Immersion/Hypothermia - Survival and Rescue
Kent Benedict, MD, FACEP
"For this relief much thanks; 'tis bitter cold,
and I am sick at heart." - William Shakespeare, Hamlet, Act 1
The challenge of sailing small vessels is simply this: to get us from one point to another over the
water without adding to the discomfort or potential disaster by actually putting us into the water.
Especially cold water. This is not to say that swimming, kayaking, diving, surfing and all the other fun
things one can do in the water should be avoided, but for our simple goal of getting our boat from here
to there, staying warm and dry are our paramount concerns.(*see sidebar on being swept overboard)
Which brings us to the point of this article.
Immersion hypothermia is the medical term for one of the bad consequences of falling into cold
water. Obviously, drowning or near-drowning is the other consequence. The definition of cold water is
variable but the significant risk of immersion hypothermia is in water 77 degrees Fahrenheit or colder.
Just looking at the temperatures of the San Francisco Bay shows us that in our area the risk is universal
all year long.
San Francisco Bay Average Water Temperature(Degrees Fahrenheit)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
52 52 54 54 54 54 56 56 54 54 52 52
It is estimated that half of all so-called 'drowning' victims actually die from the fatal effects of
cold water. Cold water robs the body of heat 25-30 times faster than air. When you lose enough body
heat to make your temperature subnormal, you become hypothermic.(*see sidebar on signs and
symptoms of hypothermia)
So what actually happens when you fall overboard into 50 degree water? When the water first
hits you, it's cold but not paralyzing. If you're wearing a PFD, and you survive the first few minutes in
the water, there's a good chance of surviving up to four hours. But it can be extremely variable,
depending on sea state, your physique, your conditioning, your clothing, and ultimately your behavior in
the water. But the first minutes in the water are critical. The moment you go in there is a gasp reflex,
causing an involuntary mouth opening and deep inhalation. If you are actually under water when that
gasp occurs one of two things will happen: in 10% of us the larynx goes into spasm and nothing can
enter the lungs, and suffocation may occur. In the rest of us there is an almost immediate flooding of the
lungs and drowning begins. Loss of consciousness rapidly follows and soon death. As Sebastion Jungar
wrote in his book The Perfect Storm, The panic of a drowning person is mixed with an odd incredulity
that this is really happening. Having never done it before, the body - and the mind - do not know how to
die gracefully. The process is filled with desperation and awkwardness. "So this is drowning," a
drowning person might think. "So this is how my life finally ends." If the gasp reflex were not bad
enough, there is yet another reflex which for some can be even worse — cold water causes a precipitous
rise in blood pressure and heart rate. In some, this creates such a strain on the heart that it literally stops
pumping blood. Unconsciousness and death occur almost instantly. For those who have had the good
fortune of surviving those first minutes without immediately drowning or having a cardiac arrest, they
now face the challenge of staying alive long enough for rescue. But the cold water is making it more and
more difficult. Blood is rapidly shunted away from the surface of the body in order to protect vital
organs such as the kidneys, liver, brain, and heart. Uncontrollable shivering begins. Muscle coordination
and strength wane. Studies have shown that after the first five minutes in 50 degree F water, muscle
strength decreases by 1.8% per minute.(*see sidebar on muscle fatigue). Disorientation and confusion
begin. It becomes harder and harder to think straight. The hands are now numb and unable to grip. The
legs are so weak that any attempt to swim or even tread water is useless. And even if the sea is
moderately calm and the PFD is maintaining the head above water, the constant splashing of small
waves makes it impossible to keep water out of the nose and mouth. If rescue does not happen soon,
death is inevitable.(*see sidebar on the Titanic)
Okay, now that I've painted such a fatalistic picture, let me try to get you out of this mess.
Fortunately, the whole issue of cold water immersion has been extensively studied and from those
studies we can give reasonably good advice based on solid evidence. But first of all, it is important to
understand that there is at least one factor which you have little control over — your physique. Children
are especially prone to hypothermia because of their high skin surface to body mass ratio. And for the
same reason, tall skinny people are far more susceptible to hypothermia than short, fat, or highly
muscular types. As an example, in July 1993 in the Straight of Georgia, Canada, a man fell off a ferry
into 61 degree F water. He had no PFD. The predicted survival time in that water is around five hours.
But he drifted overnight, over 8 hours, and was rescued in the morning. He was found to be only
moderately hypothermic. And although the media heralded this event as a 'miracle', it could better be
described as not that unusual - the man was a well muscled 6'4", 220-pounder. His bulk of muscle and
fat made him a slow cooler, and he survived.
But what factors can you control if you do happen to fall into cold water? Above all, don't panic!
Panicking exhausts your reserve energy and strength. There is a physiologic reflex to hyperventilate in
cold water. Try to consciously slow your breathing. Hyperventilation can quickly produce muscle
cramping and spasms.
And then try to remember the following:
• Keep wearing all your clothing. Do not remove anything unless possibly your seaboots if they
are weighing you down and pulling you under.
• Button, buckle, zip and tighten collars, cuffs, shoes and hoods. Do this quickly, before your
hands are numb and muscle strength is gone. Cover your head if possible. A layer of water trapped
inside your clothing will be slightly warmed by your body and will help insulate you from the colder
water, thereby slowing body heat loss.
• If you were not wearing a PFD when entering the water, there is a chance an alert crew has
tossed one overboard. Find it and put it on immediately.
• Look for a nearby rescue line or float and swim to it if at all possible.
• At this point devote all your efforts to getting out of the water and continue to act quickly
before you lose full use of
your hands and limbs. Climb onto anything floating. The object is to get as much of yourself out of the
water as possible. Even though you are now exposed to wind and spray, you will not lose heat as rapidly
as you would in the water. "Wind-chill" is not anywhere near as lethal as staying in the water.
• Do not attempt any further swimming unless it is absolutely necessary to reach a nearby boat or
another person. Unnecessary swimming "pumps" out warmed water between your body and your
clothing causing new cold water to take its place. Excessive movement of your arms and legs can reduce
your survival time by as much as 50%.(*see sidebar on Dancing Ledge)
• If there is no floating object nearby to hold onto, then assume the Heat Escape Lessening
Position (H.E.L.P) by holding knees to chest. Wrap arms around legs and clasp hands together.
• If there are others in the water, huddling together can extend survival time up to 50%.
• Continue remaining as still as possible. It may be painful but remember that intense shivering
and severe pain are natural body
reflexes in cold water which will not kill you. Heat loss will.
For those of you who are still on-board and are now going to be assisting in the rescue, I offer
the following advice:
• The first principle of rescue is to get the victim out of the water as soon as possible.
Immediately throw into the water anything that the person might be able to wear or hang onto. Make
sure that at least one crew watches the victim at all times. Get the boat back to the person using
whatever technique you have practiced in your man-overboard drills.
• After the first 5-10 minutes do not expect the victim to able to get out of the water unassisted.
After 15 minutes, assume the victim is already significantly hypothermic and will be helpless to assist in
his own rescue.
• Remove the victim from the water gently and in a horizontal position. Even mildly
hypothermic victims, if forced into a vertical or standing position, can suddenly drop their blood
pressure and lapse into unconsciousness.(*see sidebar on post-rescue dangers)
• Gentle handling of the victim is extremely important since excessive jostling can produce lethal
heart arrhythmias in the moderately hypothermic person.
• If the victim is unconscious, not breathing, and no pulse, then CPR is indicated. But, before you
start CPR you must make absolutely sure that there is neither pulse nor breath. In severely hypothermic
victims, respirations and pulse may be slow, shallow, and difficult to detect. Therefore, take at least a
minute in assessment before commencing with CPR.
• You may have to continue CPR for a long time. A few years ago, a severely hypothermic 25
year old woman was rescued in the Sierras. During transport she suffered a cardiopulmonary arrest but
was successfully resuscitated after 3 hours of CPR.
After recovery from the water and initial management of any life-threatening emergencies the
objective is the prevention of further heat loss.
• Minimize physical activity. The physiologic process known as "afterdrop" produces further
cooling of the body long after removal from the water. This can be aggravated by physical activity
where the cool body surface blood is suddenly mixed with the warmer core blood. Experiments on
moderately hypothermic volunteers have demonstrated a threefold greater afterdrop during treadmill
walking than when lying still.
• Remove wet clothing, gently dry the skin, and then wrap the victim in a dry insulated blanket,
rescue bag, or sleeping bag. If further heating of the victim is warranted, then the safest method is
"buddy warming" where a crew member joins the victim in the blanket or sleeping bag. The buddy
should concentrate on lateral chest to lateral chest contact. Lower extremity contact is unnecessary so
pants don't have to be removed.
• Avoid using heating pads or hot water bottles because of the high risk of further skin damage.
Hypothermic skin is injured skin and there have been cases of third degree burns resulting from their
use. If it is felt the devices must be used it is mandatory that they not be in direct contact with skin. Use
clothing or blankets as a barrier.
• Do not give hot food or liquids unless the victim is fully alert and awake. There is a strong
vomiting reflex in hypothermia. The drinks and food may help the morale of the victim but are only
minimally effective in raising the temperature.
• No alcoholic drinks, cigarettes, or coffee in any hypothermia situation.
Ultimately, any person who has suffered anything more than a very minimal cold water
immersion should be brought to medical attention as soon as possible. There are many case histories of
death occurring hours after the incident.
Signs and symptoms of hypothermia
• Minimal/moderate hypothermia: Body temperature has dropped below 96-97º F, but is
still above 90º F. The victim feels cold, is quiet and reluctant to communicate, shivering is prominent.
• Moderate/severe hypothermia: Body temperature now is between 90º F and 85-86º F.
Victim is semiconscious, movement is slow and uncoordinated, muscle rigidity has set in and shivering
• Severe hypothermia: Body temperature is below 86º F and the victim is unconscious,
pupils are dilated, there is depressed breathing, and a high likelihood heart arrhythmias. The victim often
• The 3 best rapid clinical signs to determine degree of hypothermia are 1) Skin
temperature of the back: if warm, then hypothermia is usually not present. 2) Shivering: Starts when
body temperature drops below 95º F, stops somewhere around 90º F. 3) Mental status markedly
deteriorates below 90º F.
On being swept overboard
"The most dangerous position is on the foredeck, shifting jibs or setting or lowering spinnakers (but)
where most accidents take place is in the comparatively safe position of the cockpit, when safety belts
are temporarily detached when changing helmsmen, or when a man emerges from below to empty a
gash bucket, to be sick or to come on watch." - K. Adlard Coles Heavy Weather Sailing
I would also add to Coles' thoughts — taking a piss over the side of the boat can be a high risk
proposition. Often when the dead body is recovered, the pants are found with the fly open.
The story of Dancing Ledge
On Sunday, the 29th of July 1956, in a Force 11 storm(winds 56-63 knots), the 10 ton cruising yacht,
Dancing Ledge, foundered in the English Channel only a mile from land taking three of her crew to their
deaths. The sole survivor of the tragic event, Mrs. O'Sullivan, wrote — "We were pooped almost
immediately. Water broke through the starboard cabin top combing, which burst inwards. Two or more
seas heaping together spilled a few more tons of water on top of us, and Dancing Ledge went down very
quickly. I was in the cabin, which seemed to fill from every direction...We hit the bottom or something
hard...In the cabin full of water, and dark, I got free by wriggling my feet out of my shoes and groped
out...The life jacket took charge once I got into the cockpit, and I went up fast for a long, long way."
Mrs. O'Sullivan, Colonel H. Barry O'Sullivan(her husband), and one other crew(the fourth crew had
apparently already died) soon found the vessel's upside-down dingy floating nearby. The trio clung to
the dingy over four hours before a rescue vessel appeared. According to Mrs. O'Sullivan, "Barry insisted
we should 'bicycle' continuously with our legs in order to keep warm and to avoid stomach cramp..." A
British navy frigate, H.M.S. Keppel, approached at about this time. Colonel O'Sullivan took off his
orange jacket to wave it above the spray to attract attention. With extreme difficulty the frigate was
maneuvered alongside and a rope was thrown to Mrs. O'Sullivan. She let go of the dingy with one hand
to grip the rope. Her hand was so cold and rigid that she could not close it around the rope. She let go of
the dingy with the other hand to attempt to get a stronger grip, but it was impossible to hold the rope and
it ran through her hands as a wave, deflected by the bulk of the frigate, swept her along the length of the
ship and she drifted away into the clear. Now supported only by her life-jacket, she became
unconscious. Within a few minutes the ship sent a rescue swimmer, secured by a lifeline, into the water
where he was able to bring the comatose woman back to the ship and carry her up the scrambling nets.
Once she was aboard, the search for the others continued, but the ship could find no trace of them or the
At approximately 11:40 PM on April 14, 1912, the Titanic struck the iceberg and the ship sank in calm
seas. The water temperature was near 32 degrees F. Of the 2201 people on-board, only 712 were
rescued. A rescue vessel had arrived with two hours of the sinking, yet 1489 people died in the water.
Nearly all were wearing 'life preservers'. Although the official cause of death was listed as 'drowning',
the most probable cause was immersion hypothermia.
On the dangers of the post-rescue period
"I was the last man to be picked up. Everyone was conscious when taken out of the water but many of
the men lost consciousness when taken onto the warmth of the trawlers. Nine of the men died on board
soon after being picked up. We were all given a small mouthful of spirits... and this made us sleep, and
these unfortunate men went to sleep and did not wake up again" — Captain H.J.M. Downie of the SS
Empire Howard which sank in 29 degree F water in the Arctic Ocean
On muscle fatigue
"I was pulled out of the water into the boat.... I had by this time been in the water about 2 1/2 hours, the
temperature of which was 47 degrees F, and my body was completely numb when rescued" — Captain
F.D. Straus of the SS Manchester Merchant in the North Atlantic
Dr. Benedict is a board-certified emergency physician and USCG Licensed Master. From 1980 to 2002
he was the Chief Medical Officer for the California Maritime Academy's training ship, USTS GOLDEN
BEAR. He holds the appointment of Clinical Associate Professor of Medicine at Stanford. He has taught
Emergency-Medicine-at-Sea courses for years, written articles for Latitude 38 and authored the medical
chapters in the standard US Maritime texts the American Merchant Seaman’s Manual and the Merchant
Marine Officers’ Handbook. He cruised extensively on his own vessel, the San Juan. Currently he is the
Medical Director of Emergency Medical Services in Santa Cruz and San Benito Counties. In his spare
time he is a Caribbean charter captain.
For further information or consultations call (831) 662-0668 or e-mail email@example.com