Water conducts heat 25 times faster than air because it has a greater density which is why you lose body heat a lot faster when in water. The normal temperature of a human body is at a steady 98.6°F. The circulatory, respiratory, and nervous systems begin to slow down as your body temperature drops below normal. Mild hypothermia begins to set in between normal and 96°F while Moderate would fall between 92-96°F, and severe would begin below 92°F. If your core temperature falls below 86°F, death is imminent.
In context, your survival time is between 15 and 45 minutes before you would drown in a lake that is 32°F, unless of course, you are a mutant and have superpower genes like Lynne Cox who swam to Antarctica without a wetsuit. On the other hand, you could survive between 1 to 6 hours in the same lake at a temperature between 50 and 60°F.
Know Your Limits
So a couple of questions, how cold is too cold? There isn’t a simple one-size-fits-all answer but a good rule of thumb is water needs to be above 50°F in temperature for outdoor open water swimming. Many triathletes would not go open water swimming unless the water temperatures were north of 60°F. Consult your General Practitioner before attempting cold water swims especially if you have a heart condition or asthma. Know your limits and don’t forget to check lake temperatures at NOAA.
Regardless of how strong or experienced you are, you are not immune to the dangers of swimming in cold water. After the initial shock upon contact, you will experience shortness of breath but you should feel better after a few minutes of swimming. If you start to feel confused, grow colder as you swim, or if your muscles feel weak, get out immediately. Learn to spot the signs in yourself and others, too. Pale skin, drowsiness or slurred speeches are not good signs. Okay, then what can I do to alleviate the effects or avoid drowning?
Acclimatise: The simplest solution is to take cold water showers for a few weeks before your swim. Swim often, at least once a week, two or three times preferably, familiarize yourself with the sensation. The more you swim in the cold the less you will notice it, although you should avoid going for cold water swims alone.
Build Slowly: Cold water combined with any currents demand more energy and can quickly sap your strength. So don’t push yourself too hard by having unrealistic expectations trying to swim the same distance or duration that you can in the pool. Begin slowly and the increase the length or duration with time.
Cover yourself: A wetsuit, swimming cap and neoprene swim socks will keep you considerably warmer in the water. Invest in a full body coverage triathlon suit to prevent heat from escaping your body making your swim less torturous. Wear a cap, maybe two. Neoprene caps work better than standard latex to help keep your head warm. Neoprene socks are also a good idea, but they can be a hassle when transitioning to your bike on race day. Earplugs, some swear by them but they can be useful in extremely cold water to maintain your core temperature.
Warm up: At most races you end up getting there early and end up standing around a lot. If the temperatures are low, stay in your dry clothes as long as possible or get into your wetsuit, cap, and zip up; a very efficient way of staying warm instead of standing around in your trisuit and consuming your energy to stay warm. Drinking warm liquids before the swim can also help raise your core temperature.
A ten minute warm up of exercises and stretches before getting in the pool will also reduce the shock from the water on your muscles and prevent them from contracting as much. Getting into rhythm will be easier too.
Slowly Wade In: Never jump or dive in as your first contact with cold water will be a shock and your body’s natural response will be an involuntary gasp resulting in shortness of breath, a phenomena known and creatively so as Cold Shock Response. Diving in or going head first means you have this involuntary reaction with your head under water, which could result in drowning. Slowly lowering yourself or wading into the water helps prevent any inhalation of water into your lungs during this period. Although do not linger to assess the cold or admire the view as you waste precious body heat and energy.
Blow Bubbles: After you lower yourself or wade in waist deep dip your face in the water a few times to absorb the shock before you start swimming. Blow bubbles as you immerse your face, sounds silly, but bubbles work.
Focus on Your Breathing: You are going to shiver. So, instead of focusing on your body’s natural reaction focus on your breathing. When there is a cold shock the inhale reflex affects your exhaling, which dovetails with our previous point, blowing bubbles means you exhale. Focus on emptying your lungs so you can inhale more efficiently.
Keep moving: The faster you swim the quicker your heart will beat and the quicker blood will be pushed around your body which helps abate the continual decline of your core temperature. Don’t push yourself too hard either and if you have to stop catch your breath, never completely freeze movements, tread slowly using your legs to keep your blood pumping.
Right Recovery: Your core temperature continues to decline even after you get out of the water. Going straight into a hot bath or shower causes blood vessels to open too quickly and the sudden drop in blood pressure results in poor circulation to major organs increasing your risk of anything from fainting to cardiac arrest. Avoid the temptation of a hot bath and chang into dry clothes and keep moving. A warm drink also helps regain your regular body temperature safely.
Most importantly, practice, stay safe and have a good time.