As discussed "How to Reap the Benefits of a Good Warm-up", a proper pre-race warm-up is one of the most important preparatory measures you can take to ensure a great swim.
While Masters meets usually provide a separate warm-up pool for swimmers, open-water events are not always as accommodating, and convenient warm-up conditions are hard to come by. Below is a breakdown of several creative ways you can prepare for an open-water competition should ideal warm-up options be limited.
Since most triathlons and ocean swims begin very early in the morning, my previously suggested wake-up swim (two to three hours before your event) is probably not going to happen. Not only would you have to wake up around 4 a.m., but you would have to find a pool open at that hour to do a few laps. Not likely, and you are better off getting the additional sleep.
However, a quick, warm shower the morning of your race can serve as a wake-up call while getting your circulation going. Make sure the water is very warm (not hot), and only stay in about three minutes (any longer and you will end up feeling too relaxed and drained).
Arriving at the Race
Once you get to the race site, allow yourself enough time to warm up, regardless of whether or not you plan to swim before your race. There is a lot you can do in 45 minutes to prepare your body for competition even if you avoid loosening up in the water. Give yourself plenty of time, no matter what you choose to do. If you arrive at the race site late only to have to wait in lines to register or check in, you will waste valuable pre-race time and cause yourself unnecessary stress.
First and foremost, check the temperature in the body of water where you will be competing and decide if you can tolerate warming up in it without shivering yourself into a hypothermic state. Each individual has a different tolerance depending on their physiological make-up, and you need to decide for yourself even if you see plenty of other swimmers in the water (remember, you may be lean, but they may have an advantageous extra layer of insulation!).
If you can get in the water comfortably, it is definitely a good idea. A wetsuit will help you stay warm, and if the event allows wetsuits in competition you should certainly wear one while warming up to get a feel for it. Swim about 100 easy strokes (equivalent to about 100 meters), then turn around and repeat the drill at a medium pace. Do this twice (total: about 400 meters). Then, do a few dozen strokes on your back to stretch out your shoulders and a few dozen breast-strokes to warm up your legs.
Make sure you are not tightening up your body in response to the water temperature. If you are, it defeats the purpose of warming up and you should exit the water in favor of a dry-land warm-up.
Assuming you stay in the water, do a few explosive 25-stroke sprints to get your heart rate up to 85 percent of your max, and swim down until your pulse is back to normal active rest.
When you feel loose, alert and ready, consider your warm-up complete and exit the water, drying off and donning a pair of sweats to keep your body warm (if you are shivering, your muscles will revert to being tight and thus cancel out your warm-up!).
A Waterless Warm-up
If you decide the water is too cold to warm up comfortably, you may opt to stay dry and do some basic stretches and pulse-quickening activities in the time before your race. Start by doing arm swings, an exercise where you spin your arms from the shoulder (one arm at a time) either forwards or backwards. This not only stimulates blood flow and increases circulation, but stretches out sleep-constricted muscles in a gentle way, avoiding injury. A typical arm-swing warm-up set:
10 x left arm swings forward
10 x right arm swings forward
10 x left arm swings backward
10 x right arm swings backward
In addition, try swinging your arms horizontally from side to side, simultaneously. If done correctly, at one end of your stretch you should be embracing yourself while at the other end of it your arms are extended behind your back as if you were trying to touch, or clap, them.
Rotate both shoulders in a clockwise and then counterclockwise motion a few times with your arms at your sides. Hunch your shoulders, extend them, and move them around to get the blood flowing.
Do a light jog, maybe a quarter-mile or two minutes' worth, stop, and stretch some more. Jog another few minutes until you feel warm, but not sweaty or fatigued. The idea is to get your heart rate up above normal and sustain it above your resting rate prior to competition.
Making an Entrance
Immediately before you start your swim, it is indeed a good idea to enter the water even if it is cold. In such extreme temperatures I prefer to accustom my body to the shock rather than have to deal with an ice-cream headache early in the race.
In addition, your lungs natural reaction to cold water is to constrict at the shock, causing you to hyperventilate (pleasant, huh?). By placing yourself calmly in the water you can allow your breathing to stabilize rather than deal with such extremities at the start of the race.
Just make sure to literally enter the water with barely a minute to go before the start, so that you don't stand outside in the wind for more than you have to before the gun goes off.
Inevitably, when you hear the starting gun, the adrenaline rush will overcompensate for any nerves or shivers you have, and racing in the cold will be the least of your concerns. With a proper warm-up you'll be ahead of the game and primed for a great race.