Tips for Cold Water Swimming

[Guest Post] courtesy of Andrew W.

Luca Pozzi
Stile Libero
8 min readNov 11, 2020


“Swimming gave me a sort of joy, a sense of well-being so extreme that it becomes at times a sort of ecstasy. . . . The mind can float free, become spellbound, in a state like a trance. I have never known anything so powerfully, so healthily euphoriant — and I am addicted to it, fretful when I cannot swim.” — Oliver Sacks

The swimming addicted among us are probably starting to worry about the dropping water temperatures and wonder how we’ll get our fix when it gets cold. The only answer, of course, is to keep swimming. To help, I wanted to share some learnings and tips I picked up the past 7 years I spent swimming year-round, without a wetsuit, in the San Francisco Bay. First, though, a quick note on what happens to our bodies in the cold water and hypothermia which can happen to inexperienced swimmers even in the current water temps:

When we immerse ourselves in cold water, our core temperature will drop from outside-in. As we breathe through our mouths while we swim, we further cool our core from inside-out. While we try to reheat ourselves after, via sweaters or a hot shower, for some the immediate vasodilation effect can lead to feelings of weakness and lightheadedness with the body core still being lowered. This is known as “afterdrop” and it is often a fall, at this point, that can cause serious injury. Essentially, your body will circulate less blood to your extremities and skin when swimming to keep the core warm. Once you get out and drink something warm, put on a sweater your body will think its “warm” and will start circulating the warm blood from the core back into the cold extremities which in turn will bring down your overall temp after the swim and could result in hypothermia.

Cold Water Swimming Tips:

  1. Know the signs of Hypothermia: The obvious is being cold and shivering but it’s hard to see that in yourself. If you feel confused (can’t do simple math in your head), feel “warm” all of a sudden after feeling cold, get euphoric then tell somebody and get out of the water. If somebody tells you they are cold and needs to get out, go with them.
  2. Caps: Wear two caps. Silicone caps are good but if you are prone to getting cold consider getting an insulated neoprene Pbear cap (you can wear a silicone on top of a Pbear too).
  3. Earplugs: Keeping cold water out of your head makes a huge difference as well. Wear earplugs and cover your ears with your cap(s). Wearing earplugs also helps to prevent surfers’ ear.
  4. Movement: The most dangerous thing you can do is to stop moving in cold water. This is like your body turning its furnace off in the middle of winter. Keep moving in the water. I suggest we break into pods (based on speed and desired duration) at the beginning of the swim so that groups of different speeds can keep moving without waiting for everyone while also ensuring people aren’t swimming alone. Also, if you are wearing earplugs you can’t hear what others are saying so no point in pausing to chat anyway ¯\_(ツ)_/¯
  5. Eating: Eat something before you swim, even if it’s not a full meal. It’s counterintuitive to many to eat before working out, but by eating before, you get the blood circulating to your gut that helps keep your core warm. Bonus points for eating something warm and hearty like oats with granola and peanut butter.
  6. Combined Temps: The combined air and water temp is really important since half of your body is out of the water when swimming. NOAA buoys are a great source for this kind of information. For context, 130 will be cool and anything below 120 will be cold. The SF bay for example gets a few <100 (sub 50 air and water) days each year and that’s very cold (but doable if you are acclimated).
  7. Acclimation: Try to be consistent with your time in the water, especially as it cools down and start short. Once it’s cold, don’t try to increase your time in the water by intervals more than 10 minutes per week. It typically takes 2 weeks of regular (4 day a week) swimming to get your initial acclimatization. In cold water, a 30 minute swim is a lot.
  8. Warmup: Get the blood pumping before you go in. Spend 5–10 minutes doing jumping jacks, squats, etc so your core temp is elevated before you enter the water.
  9. Post-Swim: Dry off and put sweats and a beanie on quickly. Take off your cold and wet suit quickly (deck change). Cover your head and feet to keep the warmth. Bring a thermos or milk jug of warm (not hot or it will be scalding) water and a tray or bucket to pour it into to and stand in it (like this) for a few minutes after swimming to help warm you up. Bring another thermos of a warm (not hot) liquid to drink afterward as well to warm your core. If you go home and take a hot shower you will feel itchy all over and your skin will be blotchy and purple since blood hasn’t been circulating to it properly. Warm up the shower slowly.
  10. Car Sauna: Someone should take turns either not swimming or getting out early and start cars in advance to blast the heat/seat heaters. Don’t drive if you are too cold. You may get afterdrop at this point and start shivering and shaking like crazy even though you are bundled up and in a warm car.
  11. If you do get cold: Don’t push it, tell somebody, and get out quickly where you can (eg on the beach even if you aren’t back to the pier).
  12. Getting In: Not so much advice as a mantra. Remember, you’ll be glad to have done it when it’s over and there’s no point in dilly-dallying since the water isn’t getting any warmer :)

Simplistically, there are four progressive stages of a cold water swim. These stages can be plotted by their relationship between discomfort and actual coldness. A common misconception is that discomfort = actual coldness. As you will see, you can be uncomfortable without being cold and hypothermic without being uncomfortable. It’s important to know your own relationship to these stages to ensure a safe swim as well as be able to accomplish what you are actually able to do. The stages are:

  1. Getting in: This stage is always high in discomfort yet you aren’t yet actually cold. It’s simply the shock of the cold water that’s uncomfortable vs. being deeply cold in your core.
  2. In the Groove: This is what happens when you start going and your body is still sufficiently warm and you are generating energy by swimming. The more acclimated you get, the longer this phase becomes as your progression down the actual cold axis will be slow thanks to your acclimatization. For others with different acclimatization and physiology, this phase can be very short.
  3. Ready to be done: This is the phase of the swim where you know you are cold and are getting progressively more uncomfortable. Signs of this phase are often “the claw” (the inability to close your fingers due to loss of dexterity), stiffness in your hip flexors, slurring words, chills to your core, and a longing desire for something warm. This is the phase where you should start making your way back to shore.
  4. Hypothermia: If you push yourself past ready to be done, you may feel better, a sense of euphoria and not cold. This is an extremely dangerous place to be as it’s your body becoming Hypothermic. If you can no longer do simple math in your head or lose focus on basic things you need to get out.

Caveat: these are broad generalizations that oversimplify the uniqueness of individuals and their environments and should be taken loosely. For example, many long distance swimmers will feel progressive waves of cold while in their “in the groove” stage but are experienced enough to know that they aren’t actually cold. Conversely, inexperienced swimmers may never have an in the groove stage and will immediately be truly cold and at risk of Hypothermia.

Swimming in cold water when done right is an amazing, liberating experience. It’s a silver lining to pools being closed that so many more people will now discover this great joy. Even with a short swim, you will feel the warm, accomplished sensation in your body that you get after a really hard workout in the pool and feel great all day.

Lastly, I will leave you all with some hopefully inspiring content to try to reverse any fear from the above.

See you in the water soon.


The Author

Andrew is an avid open water swimmer, swimming year-round in the San Francisco Bay and Long Island Sound. He has swum the Catalina Channel, the width of Lake Tahoe, and Bay to Breakers. However, Andrew’s favorite swim is “Bruno Point” in San Francisco with good company, followed by a long sauna and Bob’s donut.

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