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Feature—February 2008
Cold Shock and Swimming Failure
The real danger of cold water is not in the slow descent into hypothermia, but in the sudden symptoms of
cold shock .
by Chris Brook s
It is we ll k nown by m ost se a k ayak e rs that hypothe rm ia is a se rious risk . Ge tting chille d by e x posure to wate r
e ve n a s warm a s 70°F (21°C ) can e ve ntua lly le a d to a num be r of se rious a nd e ve n life -thre a te ning physica l
a nd m e nta l sym ptom s. Many k ayak ing book s focus on the various sta ge s of hypothe rm ia , a nd while it is
im porta nt to re cognize the m , the m ost se rious a nd dange rous e ffe cts of cold wate r are n’t in a slow
de te rioration of abilitie s. For k ayak e rs, a m ore re alistic approach to the risk s of cold-wate r im m e rsion is to
focus on the e ffe cts that happe n in the first se conds of im m e rsion and the following fe w m inute s.
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W ate r doe s not ne e d to be drastically cold to k ill you. You can drown ve ry quick ly if you are not m e ntally and
physica lly pre pa re d for sudde n im m e rsion. Since e a rly tim e s, the Inuit unde rstood this dange r. The wate rproof
paddling jack e ts—tuiliqs and kamleikas—used by e a rly k a yak e rs se a le d toge the r with the ir k a yak s to provide full
body cove rage . Inuit whale rs e ve n de ve lope d dry suits. The y consiste d of se alsk in or se al gut stitche d toge the r
to form a com ple te cove ring that was worn by harpoone rs hunting whale s from umiaks. The dange r of e x posure
to cold wate r was we ll unde rstood by the Arctic m aritim e pe ople s.
The presence of icebergs makes it obvious that kayakers should dress for cold w ater. On a w arm summer day, w hen it
may be comfortable to paddle in shorts and T-shirts, the risk of cold w ater may still be present, and dressing for the
w ater is essential.
The Gre e k author He rodotus wrote about hypothe rm ia back in 450 BC during the Pe rsian/Gre e k wars
com m e nting on m arine rs who die d in se a battle s in the Me dite rrane an Se a: “Those who could not swim
pe rishe d from that cause, othe rs from cold.” The first hum an e x pe rim e nt in cold wate r to te st out the value of
prote ctive clothing, howe ve r, was not done until 1922. A doctor work ing for the Me rchant Shipping Advisory
C om m itte e on life saving appliance s, nam e d Dr. Hill, im m e rse d his laboratory assistant, Mr. Pe rgarde , in 62°F
(16.6°C ) wate r and conclude d: “That the cove rings we t or dry, prote ct a body from cooling down, and also that
a rubbe r sk in outside such cove rings is a furthe r gre at prote ction.”
The four sta ge s whe re de a th can occur a s a re sult of sudde n cold-wa te r im m e rsion have be e n re cognize d by
the scie ntific com m unity since be fore W orld W ar II. These are : C old Shock —k ills in 3–5 m ins. Swim m ing Failure
—k ills in 5–30 m ins. Hypothe rm ia—k ills afte r 30 m ins. Post-R e scue C ollapse —k ills during or hours afte r re scue .
The first two stage s of im m e rsion—cold shock and swim m ing failure —k ill m ore than half the pe ople who drown.
It’s e spe cia lly im porta nt to prote ct yourse lf from those first two sta ge s, a nd to do tha t e ffe ctive ly, you ne e d to
k now som e thing about cold-wate r physiology and survival psychology. It’s also im portant to unde rstand the
de nial of risk that is built into us all and cause s m any se a k ayak e rs to paddle without we aring prote ctive
clothing or fail to m ak e good plans and pre paration prior to -launching. Up until about 50 ye ars ago, no one
re a lly unde rstood the re a son why pe ople sudde nly im m e rse d in cold wate r die d. It was a ttribute d to a n ina bility
to sta y a floa t a nd vague te rm s such a s “e x posure .” The ste a dy loss of live s was sim ply a cce pte d a s fate a nd
an occupational hazard.
As long a s cold shock a nd swim m ing failure we re conside re d only of a ca de m ic inte re st, m arine rs a nd
gove rnm e nt re gulators—and late r survival training schools, outdoor-sportswe ar m anufacture rs and PFD
m anufacture rs—conce ntrate d the ir e fforts on prote cting pe ople from the m ore protracte d proce ss of
hypothe rm ia . As a re sult, hypothe rm ia is wide ly re cognize d a nd unde rstood; howe ve r, e ve n with today’s we ll
e stablishe d te aching program s, good re gulations and m uch im prove d life -saving e quipm e nt, the two stage s of
im m e rsion have ofte n be e n ove rlook e d. The se a re wha t I want to a ddre ss.
Cold Shock
O ve r 15 ye a rs a go, Moulton Ave ry wrote a n e x ce lle nt a rticle in this m agazine (“C old Shock ,” SK, Spring ’91),
noting that “im m e rsion in cold wate r k ills m ore se a k ayak e rs than any othe r factor in our sport.” C old shock
has be e n observe d in pe ople se nsitive to cold a t wate r te m pe ra ture s a s high a s 77°F (25°C ). In wate r be low
60°F (15°C ), the e ffe cts of im m e rsion be com e significa ntly life -thre a te ning to e ve ryone . The lowe r the
te m pe ra ture , the m ore se ve re the sym ptom s. The e ffe cts of cold shock a re com ple te ly out of your conscious
control. If you don’t prote ct yourse lf from cold wate r, the y will happe n to you whe the r you lik e it or not. If you
re ally don’t be lie ve that it will affect you, the ne x t tim e you tak e a showe r, turn the cold wate r on full blast and
aim it at your be lly button. You will soon be a be lie ve r.
C old shock is cause d by rapid sk in cooling and can k ill within thre e to five m inute s afte r im m e rsion. O n initial
im m e rsion, you m ak e a huge inspiratory gasp. Be ing im m e rse d in ne ar-fre e zing cold wate r is also e x tre m e ly
painful, and the sudde n se nsation of acute pain can acce ntuate the inspiratory gasp. The gasp is followe d by
se vere hype rve ntilation: a fourfold incre ase in your bre athing rate . It is not uncom m on for you to be panting at
a bre a thing rate of up to 65 tim e s a m inute in this critica l sta ge , so the re is no cha nce to hold your bre a th.
Indee d, in wate r be low 60°F, your bre ath-holding ability is re duce d by 25–50 pe rce nt. If the wate r is ne a r
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Indee d, in wate r be low 60 F, your bre ath holding ability is re duce d by 25 50 pe rce nt. If the wate r is ne ar
fre e zing, e ve n a fte r the e ffe cts of cold shock have se ttle d, you’ll only be a ble to hold your bre a th for a bout 12–
17 se conds.
The rapid bre a thing rate on its own can cause m uscle spa sm s of the lim bs a nd che st. All of these bre a thing
irre gularitie s incre ase the risk of drowning if you dip unde rwate r or have a wave splash ove r your face . It only
tak e s an inhalation of about five ounce s (150 m l) of wate r to cause drowning. Drowning is a com bination of
cardiac arre st and suffocation. Your he art stops be ating within one to two m inute s afte r you have inhale d a
significa nt a m ount of e ithe r fre sh- or se a wa te r. W ate r in the lungs com prom ise s your a bility to e x cha nge
ox yge n, and be cause re spiratory m ove m e nts m ay occur for up to five m inute s whe n unde rwate r, wate r can
continue to be drawn into your lungs.
C old shock also cause s a m assive incre ase in he art rate and blood pre ssure . The se cardiac re sponse s m ay
cause de ath, particularly in olde r, le ss he althy pe ople .
The inte nse e ffe cts of cold shock last two to thre e m inute s a nd will se ttle down a fte r a bout five m inute s of
im m e rsion. This pe riod of involuntary re actions is just at the critical stage of sorting yourse lf out afte r your
k ayak has flippe d and you’re work ing to adjust to the wind and wave s and avoid inhalation of wate r.
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Swimming Failure
Swim m ing failure is cause d by rapid cooling of the m uscle s and ne rve s and can k ill within about 5–30 m inute s
afte r im m e rsion. It is m uch m ore com m on than you’d think . It’s ofte n poorly diagnose d by inve stigators
be cause it usually isn’t possible to de lve into the pre cise history of what happe ns to a victim im m e diate ly afte r
im m e rsion. The cause of de a th liste d on the de a th ce rtifica te is com m only re porte d a s drowning. To be sure ,
drowning follows the inhalation of wate r, but it is swim m ing failure that le ads to drowning whe n the m outh and
nose can no longe r be k e pt above the surface and slip unde rwate r.
It’s ve ry dange rous to swim in cold wate r, and it doe sn’t ne e d to be that cold (just 60°F) to cause a swim m ing
failure that will drown you. Ne wspape r re ports about drownings ofte n m e ntion that the victim was “an
outstanding swim m e r, yet he only swam 50 yards and drowne d.” Your swim m ing ability in warm wate r be ars no
re lationship to your swim m ing ability in cold wate r. Profe ssor Mik e Tipton of the Unive rsity of Portsm outh, U.K.,
a nd his colle a gue s in Swe de n de m onstra te d quite cle a rly tha t your a ngle of a ttack while swim m ing (without a
PFD) incre ase s from 18 de gre e s to 24 de gre e s, and on swim m ing failure , just prior to drowning, the angle of
your body be com e s m ore upright at 35 de gree s.
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The dra g on the body a s it m ove s through the wate r a t a n incre a singly upright a ngle is incre a se d, your strok e
rate is incre ase d, and conse que ntly your strok e le ngth is de cre ase d. The cold cause s ine ffe ctive swim m ing
strok e s and a poor synchronization of the m to bre athing. This all adds up to an e x hauste d swim m e r floating
ne a rly ve rtica l in the wate r. As you raise your a rm s a bove the wate r ove r your he a d to signa l for he lp, the re is a
furthe r loss of buoyancy. A cry for he lp e x pe ls air from your lungs (as m uch as four lite rs), re m oving the last
ve stige of buoyancy k e e ping your m outh above the wate r. The re sult is that you sink be ne ath the wave s and
ne ve r re surface .
W hile swim m ing failure doe sn’t apply dire ctly to k ayak ers who m aintain contact with the k ayak afte r a we t e x it,
the “failure ” is just a m anife station of physical sym ptom s that do apply. Swim m ing failure will m anife st itse lf in
com prom ising whate ve r physical task s you ne e d to do: holding onto the k ayak , se tting up a paddle -float
outrigge r, lunging onto your back de ck and so on. W ithin a fe w m inute s afte r im m e rsion, you ge t a coldinduce d ane sthe sia that cause s a disconne ct be twe e n your brain and your lim bs and the ir position in the wate r
—you don’t k now whe re your arm s are . Your finge rs grow num b and paralyze d, so your fine m otor sk ills
de te riorate . Grip stre ngth is re duce d, and cram ps disable your lim bs. Shive ring furthe r im pairs m ove m e nt, and
panic com prom ise s m e ntal functions.
The Psychology of Survival
Survival schools have only re ce ntly starte d te aching life saving survival psychology. It’s as im portant to k now
a bout the psychology of surviva l a s it is to k now a bout cold-wa te r physiology. The work in this fie ld has be e n
pione e re d by Profe ssor John Le a ch, of Lanca ste r Unive rsity, in the U.K.
The brain usually m anage s to function ve ry succe ssfully e ve n in a whirlwind e nvironm e nt. W hat psychologists
re fe r to as “hum an inform ation proce ssing” is capable of handling a lot of de cisions in quick fashion.
Unfortunate ly, howe ve r, in life -thre ate ning situations, our brain is ve ry lim ite d in its ability to proce ss
inform ation and to re spond quick ly and corre ctly.
O ur bra in use s a n input se le ctor (also calle d a “re giste r”) to proce ss a ll the inform a tion re ce ive d by our se nsory
organs. All the se nsations, such as vision, he aring, taste , sm e ll, te m pe rature , vibration, pain and posture , are
constantly be ing fe d into this re giste r or input se le ctor by ne rvous syste m “te le phone line s.” He re the
inform ation is e ncode d and put into a ce ntral proce ssing unit, which is your short-te rm or work ing m e m ory. The
num be r of “te le phone line s” to the ce ntral proce ssing unit is ve ry lim ite d, and in any survival situation, you
should assum e that you only have one line . This m ak e s the proce ssing syste m e sse ntially a single -channe l
a na lyze r. This e x pla ins, for insta nce , why pe ople will swe a r tha t the y did not he a r a n a la rm sound whe n the y
we re com ple te ly e ngage d in som e othe r com ple x task , e ve n if the a la rm was ve ry loud. The y will be te lling the
truth be cause the ir inte rnal “te le phone line s” we re busy proce ssing the othe r inform ation and could not proce ss
any m ore inform ation.
The lim itation of the input se le ctor is one of the prim ary re asons it’s not e asy for a single pe rson to de al with a
com ple x proble m on his/he r own unde r e m e rge ncy conditions, and why work ing as a te am provide s a m uch
be tte r cha nce of surviva l. C om m e rcia l a irline s have re cognize d this lim itation a nd have introduce d cock pit
re source m anage m e nt for the ir flight cre ws to sha re in the de cision-m a k ing proce ss once borne sole ly by the
captain. Kayak e rs should also adopt this approach of sharing the re sponsibilitie s re quire d by e m e rge ncy
situations. Any re scue or capsize recove ry should be a group e ffort. The pe rson who capsize d is lik e ly to be
unde r the gre ate st stre ss and the m ost lik e ly to ove rlook protocols and to tak e inappropriate actions toward
re cove ry. Kayak e rs who a re n’t dire ctly a ssisting with a re e ntry can m onitor drift or tra ffic, gathe r othe r m e m be rs
of the group, look for place s to go ashore , e tc.
From the brain’s input sele ctor, inform ation is e nte re d into the short-te rm or work ing m e m ory whe re it is
com pa re d with othe r sim ilar e x pe rie nce s tha t m ay a lre ady have be e n e ncode d in long-te rm m e m ory a s
sche m as or routine s. The store d sche m as—routine s that have be e n le a rne d a nd re inforce d by pra ctice —are
available for com parison to any ne w inform ation e nte ring into the work ing m e m ory. The conne ction with the
sche m a provide s a quick path to de ciding upon an appropriate re sponse to the e m e rge ncy. If no sche m a is
pre se nt, a pla n of a ction has to be form ula te d using work ing m em ory a lone . Tha t’s a ve ry tim e -consum ing
proce ss and has a lim it on how m uch inform ation it can hold and proce ss in a give n tim e .
W ith e ach ne w situation, a sche m a is de ve lope d and a re sponse is ge ne rate d. This re sponse is the n store d in
long-te rm m e m ory for a m ore rapid future re sponse .
As we go through life , e x pe rie nce s from the be nign to the dange rous a re e nte re d into our long-te rm m e m ory
as se parate sche m as. W e have m illions of sche m as logge d into our brain. Most are quite ordinary and
autom atic: turning the alarm clock on be fore you go to sle e p at night, locating your toothbrush and brushing
your te e th first thing in the m orning, unlock ing the car a nd putting the k e ys in the ignition a nd so on. Som e ,
lik e de fe nsive driving te chnique s, fire drills, C PR and k ayak re scue s, are all cre ate d as sche m as and re inforce d
by re gular pra ctice . If the re is no re he a rsal of the se e m e rge ncy sche m as to ge t the m fully e stablishe d in longte rm m e m ory, the n the fine de tail in the m fade s, a nd it’s not re m e m be re d for late r use whe n it m ay be
life saving. That is why critical sk ills in our daily work and play re quire re gular re fre she r training.
This proce ss of de cision m ak ing in norm al, nonstre ssful circum stance s tak e s about a te nth of a se cond to
happe n. If no sche m a has be e n de ve lope d for such ordinary situations, the n the inform ation proce ssing is
done by the supe rvisory atte ntional syste m (SAS) in the brain. The SAS tak e s care of planning, de cision
m ak ing, trouble shooting, e rror corre ction and solving nove l proble m s. It also he lps us pe rform in te chnically
difficult or dange rous e nvironm e nts and ove rcom e strong habitual re sponse s. The SAS k ick s in whe n we ne e d
to respond to an unplanne d capsize , de cide whe the r to swim to shore or wait to be re scue d or assist an injure d
buddy crying for he lp. Howe ve r, unde r stre ss and with no sche m a to follow, the SAS is slow and tak e s 100 tim e s
longe r to proce ss inform ation com pare d to inform ation store d as norm al sche m as. In an e m e rge ncy, it can be
quick ly saturate d with inform ation and, as a re sult, be disable d just whe n it is m ost ne e de d.
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Self-Denial
Going hand in hand with our hum an inform ation proce ssing syste m , we also have a psychological prote ctive
m e chanism that “shie lds” us from som e of the stre sse s in life but som e tim e s doe sn’t do as good a job as it
should do. This is calle d se lf-de nial. W he n k a yak ing a ccide nts m ak e the ne ws, it’s ofte n the sam e story:
Paddle rs didn’t dre ss for the wate r a nd we re n’t pre pa re d for the we a the r. W ith the risk s so e a sily pe rce ived, why
did the se k a yak e rs ignore the cle a r thre a t to the ir live s? Profe ssor Le a ch has a n e x pla na tion for this. If your
life is routine ly com fortable and une ve ntful, your pe rce ption of a thre at m ay be m inim ize d by a fe e ling of
having the odds in your favor—“It will ne ve r happe n to m e .” The re sponse to an im m ine nt thre at is ge ne rally,
a nd surprisingly, one of ina ctivity a nd a failure to tak e a ny positive prote ctive a ction.
Pe ople te nd to re duce the ir a wa re ne ss of pe rsona l thre a t to a le ve l tha t the y fe e l com fortable with. The y will
also ally the m se lve s with othe r pe ople in the ir group who appe ar sim ilarly unconce rne d about the thre at. A
conse nsus that som e thing is not a se rious risk produce s a strong de sire to conform to the group. This failure
to a ck nowle dge a risk is ofte n m ade worse be cause pre pa ra tion for de a ling with a thre a t is often conside re d to
be boring, inconve nie nt and costly.
Kayak ing in wate r unde r 60°F is pote ntially ve ry dange rous, and if you don’t m ak e the appropriate plans and
pre parations, it constitute s tak ing a ve ry se rious risk .
Know Your Enemy
You m ust dre ss a ccording to the wate r te m pe ra ture , not a ccording to the a ir te m pe ra ture . W ha t you a re
we aring at the tim e of im m e rsion is critical. If it is not on you or if it’s not zippe d up and re ady for the wate r, it
won’t do the job you ne e d it to do. If you wind up in the wate r, your im m e diate e ne m y is not hypothe rm ia but
drowning. R e spiratory distre ss le ading to wate r inhalation is m ost lik e ly in the first fe w m inute s of e x posure to
cold wate r a nd occurs we ll a he a d of a ny sym ptom s of hypothe rm ia . If you a re we ll prote cte d from the cold, the
sym ptom s of cold shock should be m inim al. If you e x pe rie nce any of its sym ptom s, your obje ctive for the first
30 se conds to thre e m inute s is to k e e p your nose and m outh out of the wate r. In those first fe w m inute s, you
should be ve ry cautious about m aking de cisions about what course of action to tak e .
Precautions
You can avoid paddling in cold wate r, but for m ost se a k ayak e rs this is not re ally an option. Just re m e m be r:
O nce you start paddling in wate r 60°F or lowe r, you have e nte re d the dange r zone .
You can, in fact, a cclim a tize yourse lf to the cold wate r by tak ing daily cold showe rs for a bout thre e we e k s, which
will re duce the sym ptom s of cold shock for up to about one ye ar. For som e k ayak e rs, that m ay be part of
pre pa ring for cold wate r. It is inte resting to note tha t prisone rs a t Alcatra z we re a llowe d to tak e only hot
showe rs. By e lim inating the possibility of acclim ating to cold wate r, the prisone rs we re pre ve nte d from be ing
a ble to pre pa re for a swim to e scape . Be pre pa re d for the e ffe cts of cold shock whe n you capsize . Hold onto
your k ayak for support until you can control your bre athing be fore atte m pting a se lf-re scue or assiste d rescue .
You don’t want to risk having your he ad ge t subm e rge d if you can’t hold your bre ath.
Always we a r a flota tion de vice . The buoya ncy it provide s is e spe cia lly im porta nt im m e dia te ly a fte r a capsize
a nd we t e x it be cause it he lps you k e e p your m outh a bove wate r while your bre a thing is e rratic. The C a nadia n
R e d C ross has re porte d that 88 pe rce nt of canoe -re late d drowning victim s and 67 pe rce nt of k ayak -re late d
drowning victim s in the last 10 ye ars we re not we aring PFDs. W e ar the be st-pe rform ing PFD or life jack e t you
can find. Mak e sure that it fits we ll e nough to k e e p from riding up whe n you are in the wate r. If you can’t ge t
the waist be lt to cinch up unde r your rib cage , add a crotch strap to the PFD. Im m e rsion clothing ranging from
ne opre ne we tsuits to full dry suits will be ne e de d de pe nding on the trip. A ne opre ne cap will offe r a use ful
m e asure of prote ction—a full hood e ve n m ore , as it prote cts ne ck and e ars. If you ge t too hot, you can always
splash wate r on yourse lf and m ak e use of e vaporative cooling.
Practice capsize s re gularly, starting in warm e r wate r, the n—with caution and ve ry close to shore with a buddy, if
not a group of k a yak e rs—re pe a t the e x e rcise in colde r wate r. Pra ctice a broad range of capsize re cove ry
te chnique s. The m ore ofte n you practice e ach te chnique in safe but re alistic conditions, the m ore e ffe ctive and
re liable that particular sche m a will be whe n you ne e d to re sort to it in an e m e rge ncy.
Chris Brooks is a physician, scientist and inventor. He is the director of R&D at Survival Systems Ltd. Dartmouth, Nova
Scotia, Canada, and is an adjunct professor in the faculty of health and human performance at Dalhousie University,
Halifax, Nova Scotia. Chris wrote the report Survival in Cold Water—Staying Alive in 2003 for the Marine Safety
Directorate of Transport Canada.
R e com m e nde d re a ding: Esse ntials of Se a Surviva l, by Fra nk Golde n a nd Micha e l J. Tipton (Hum a n Kine tics,
2002); Survival Psychology, by John Le ach (Macm illan Pre ss, 1994).
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