Feeding strategy for long swims

Best Feeding Strategy for a 12km Cold-Water Swim

Challenges of a 12km Swim in 15°C Water

Swimming 12 km in ~15°C water (roughly 59°F) over 3.5 hours is a serious endurance challenge. The cold water will increase your energy expenditure – studies show you burn ~30–40% more calories in cold water as your body works to keep warmswimmingnature.comoutdoorswimmer.com. This means maintaining energy is critical, especially with only a single feed station available halfway through the swim. Cold conditions also raise the risk of hypothermia if you don’t stay fueled and insulated. With limited feeding opportunities and only minor prior feeding experience, you’ll need a carefully planned strategy to ensure you have enough fuel and warmth to sustain you from start to finish.

Pre-Race Nutrition and Timing

Maximize your energy stores before you even get in the water.For a swim of this length, carbohydrate loading in the day or two prior can top off your muscle glycogen (energy) storesdietitianapproved.com. In fact, when feed opportunities during the event are limited (e.g. a point-to-point swim with one station), loading up beforehand is extra importantdietitianapproved.com. Here’s a timeline for pre-race fueling:

• Night Before: Eat a high-carbohydrate dinner to build glycogen stores (examples: pasta, rice, bread, potatoes with moderate protein). Ensure you hydrate well throughout the evening (water or an electrolyte drink) but don't overdo fluids right at bedtime.

• Morning of Race (3–4 hours prior): Have a balanced, carb-rich mealusms.org. This could be oatmeal with fruit, toast with jam, a banana and some yogurt, or whatever familiar breakfast sits well for you. Include some protein (eggs, yogurt, peanut butter) and a bit of fat if you like, but keep fiber and overly fatty foods low to avoid GI issues. Drink fluids with this meal (e.g. water, sports drink, or tea/coffee).

• 1 Hour Before: Take a light snack of fast-digesting carbsusms.org. For example, a low-fiber cereal bar, half a bagel with honey, or a banana. If you use caffeine, this is a good time for it – e.g. a cup of coffee or caffeinated gel (~50–100 mg caffeine) about 60 minutes pre-swim to boost alertness and enduranceusms.orgusms.org. (Caffeine’s effects last a few hours, so it should carry you through most of the swim. Avoid it if you’re not accustomed, though.) Also, around this time, consider “pre-hydrating” with an electrolyte drink – about 500 ml of water with sodium ~60–90 minutes pre-startprecisionhydration.com. The extra sodium will help you absorb and retain the fluid so you start fully hydrated.

• 15–30 Minutes Before Start:Top off your tank with a final quick carb boost and some fluid. For example, eat a small handful of raisins or an energy gel (~20 g carbs) about 15 minutes before the gunusms.org. Wash it down with ~8–12 oz (250–350 ml) of water or sports drinkusms.org. This ensures you’re beginning the swim with both your blood sugar and hydration at optimal levels. (Do stop drinking at this point so you have time to empty your bladder pre-race!)

By following this pre-race plan, you’ll begin the swim with maximized glycogen stores and be well-hydrated. Essentially, you’re front-loading energy since you won’t have frequent feeds during the swim.

Mid-Swim Feeding Plan (6 km Station)

At approximately the 6 km mark (halfway), you’ll have your one chance to refuel during the swim. Plan to make full use of this feed stop – it’s crucial for a 12 km distance, as swims longer than ~10 km will significantly deplete glycogen stores and require carbohydrate intake to avoid “bonking” (running out of energy)dietitianapproved.com. Here’s how to optimize that mid-swim feed:

• Timing: As soon as you reach the feed station (around 1.5 to 2 hours into the swim, depending on your pace), take the opportunity to fuel. Don’t push on past it – you’ll need those calories for the second half. It’s typically best to take the feed before you feel completely spent; by 6 km you’ll have used a lot of energy, so refuel proactively.

• Fuel Choices: Emphasize quick, easily digestible carbohydrates and some fluid. The ideal mid-swim fuel in cold water is a combination of a carb-rich drink and perhaps an energy gel:

  • Drink: Have a sports drinkor other carbohydrate-electrolyte beverage ready (many events will let you leave a bottle at the feed station, or volunteers provide drinks). Aim to consume on the order of 200–300 ml (a cup or so) of a sports drink. This supplies fluid plus typically ~15–25 grams of carbohydrate, along with electrolytes. Critically, in 15°C water you may want it warm or at least room-temperature – if you can, use an insulated bottle or ask the volunteers to keep it warm. Swallowing a warm drink will be easier on your stomach than cold liquid and will provide a small internal heat boostdarren-miller.com.

  • Gel: In addition, take an energy gel (~20–30 g carbs per packet) either just before you arrive at the station or as you tread water at the feed. Many marathon swimmers will take a gel and then wash it down with fluiddarren-miller.com – this helps you digest the concentrated gel and gets both down quickly. If the gel is caffeinated and you’re used to caffeine, it can give you a nice boost for the second half. Otherwise, non-caffeinated is fine. Instead of a gel, you could use a few energy chews or a quick bite of an energy bar, but gels are faster to ingest.

  • Solids: Given only one stop, solid food isn’t a priority (more on this below). If you really crave something solid, keep it minimal – e.g. a few bites of a banana or a piece of a bar for psychological comfort. But priority should be on liquids/gel that deliver carbs fastusms.org.

• Calories and Quantity: In total, try to take in on the order of 150–300 calories during this feed stop. That amount would be similar to what’s recommended per hour in endurance events (about 150–300+ kcal/hour, or 30–60+ grams of carbs per hour)usms.org. Since you’re ~2 hours from the finish at this point, ~200+ calories at 6 km will help sustain you for the remaining 1.5 hours. For example, 250 ml of typical sports drink ( sports drink typically 6–8% carb) gives ~15–20 g carb (~60–80 kcal), and a gel provides ~25 g (~100 kcal). Combined that’s ~40–45 g carb (~160–180 kcal). If you can handle slightly more (say a larger drink or an extra half gel), you could push it toward 250+ kcal. The upper end might be a 500 ml bottle of a maltodextrin-rich drink (~50 g carb) plus a 30 g carb gel, totaling ~320 kcal — but only attempt that if you have practiced and know your stomach can handle it. It’s better to take a bit less and digest it well, than to take too much and feel nauseated while swimming.

• Efficiency at the Feed: Keep your stop short and efficient. In cold water, stopping too long can lead to rapid heat loss and stiffening up. Try to tread water or do a gentle breaststroke kick while you consume your nutrition, rather than just bobbing in place. Take your gel, swallow your drink, maybe burp once, and get going again. Aim for under one minute at the station. As one expert notes, to avoid getting chilled or losing momentum, “don’t spend a lot of time floating or treading water on your feed stops.”usms.org You can even rehearse in training how to uncap a bottle and squeeze a gel in quickly. The more practiced you are, the faster you’ll be back to swimming.

• Practice Ahead of Time: Since you mentioned only minor experience with feedings, trial your plan before race day. During a training swim or even a rest break in a pool, practice taking the same gel and drink you plan to use. This helps you ensure you like the taste and that your gut handles it. Sports dietitians emphasize “don’t leave fueling strategies to chance” – practice and train your gut to handle the fueldietitianapproved.com. Also practice the mechanics (opening a gel with teeth, etc.) so it’s second nature. This way, on the day, you’re confident and can execute the feed quickly.

By executing a well-planned feed at 6 km, you’ll replenish critical energy and fluids to power you through the second half of the swim.

Fuel Types: Liquids, Gels, vs. Solids

Choosing the right form of fuel is important, especially since you have limited opportunities to eat/drink. Here’s how the options compare and what’s recommended for this swim:

• Liquids (Sports Drinks/Broth): Liquids are typically the easiest to consume during an open water swim. A carbohydrate-electrolyte drink serves two purposes: hydration and energy. In a 3.5-hour swim, a sports drink helps maintain blood sugar and stave off dehydration. Because the water is cold, consider using warm liquids for comfort – marathon swimmers in cold channels often have their crew warm up their drinksdarren-miller.com. A classic choice is an isotonic sports drink (6–8% carbohydrate). You could also use a homemade mix (e.g. warm water with maltodextrin or sugar, plus a pinch of salt and maybe a dash of juice for flavor). Some swimmers in cold events even drink warm diluted broth or tea with sugar for a mix of salt, fluid, and carbs. The main advantage of liquids: easy to get down quickly, and they start digesting/absorbing immediately. The downside is they’re less calorie-dense than gels/solids, so you need a sufficient volume to get enough energy. With only one feed, make that one drink count (as discussed, ~200-300 ml of a carb drink).

• Gels and Chews: Energy gels are concentrated sources of carbohydrate (usually ~20–30 g of carbs, often maltodextrin and/or glucose/fructose, in a small 1-1.5 oz packet). They are designed for endurance athletes and are a staple in marathon swimming nutritionusms.org. The big plus is that gels are quick to ingest – rip it open, squeeze into your mouth, swallow – and you get a significant hit of energy. They’re easy to carry (you could even stash one in your suit or tuck under your cap at the start if you wanted an emergency extra, as some swimmers do). Follow a gel with a few sips of water or sports drink to help dilute it in your stomachdarren-miller.com, as gels are absorbed faster with some fluid and it prevents any throat stickiness. Energy chews or blocks serve a similar function; you’d chew a few gummy blocks to get ~30 g carbs. Those can work too, but remember you might have cold, numb fingers – tearing open a gel with your teeth might actually be easier than unwrapping chew packets. If you opt for a caffeinated gel, use it only if you’ve tried it in training (caffeine can irritate some stomachs). A caffeine boost at halfway can extend the caffeine effect through the end of your swim, which can improve endurance and mental focususms.org. Overall, for this swim, gels are highly recommended as a primary fuel due to their convenience and high energy content for the volume.

• Solids (Bars, Bananas, etc.):Solid food is generally harder to manage in a swim, but some swimmers like a little bit for longer events (>4–5 hours) to ward off hunger or for variety. Common solid-ish options in open water events include small pieces of banana, segments of energy bar, glucose tablets, or even candy. Solids usually provide a mix of carbs with a bit of fat/protein (e.g. a half energy bar might have 5–10g protein, which can help if you’re out there a very long timeusms.org). In your 3.5-hour swim, solids are optional and many would skip them. Since you only have one stop, taking time to chew is not ideal – chewing and swallowing in cold water can be uncomfortable and time-consuming. If your stomach really needs something more substantial, you could take one or two small bites of a banana at the feed (bananas are popular because they’re easy to chew and high in carbs and potassium). Just be sure to wash down any solid with fluid. All things considered, prioritize liquids and gels for this event. They will cover your energy needs without the hassle of solids. You can always have a nice meal after you finish!

Hydration Strategy

Staying hydrated is important even in a cold swim, though the strategy differs from a hot-weather event. Key points for hydration:

• Start Hydrated: Ensure you’re well-hydrated before the swim. In the hours leading up, sip fluids regularly. As mentioned, about ~500 ml of electrolyte drink about an hour before the start can top you offprecisionhydration.com. This helps you begin with a slightly elevated fluid reserve. Avoid excessive plain water chugging right before the race (that can lead to dilution of electrolytes and unnecessary pit stops). You want a good balance of fluid and electrolytes in your system.

• During the Swim: In 15°C water, you won’t sweat as profusely as in warm conditions, which means you won’t need to drink as muchas, say, a summer marathon run. Greg Shaw notes that cool water (<20°C) greatly reduces sweat rates and fluid needs compared to hot conditionsdietitianapproved.com. However, reduced needdoesn’t mean no need. You are still exercising hard for 3+ hours, and you will be losing some fluid through sweat (even if you don’t feel it) and through breathing. Swimmers often forget they can sweat in cold water, because the water keeps you cool and washes sweat away – but you do sweat and can get dehydrated if you ignore hydrationusms.org. Thus, make sure to drink at the 6 km feed. Those few hundred milliliters of sports drink will not only give you energy, but also water and electrolytes to keep your muscles functioning. This may also help prevent cramps in the latter stages.

• Electrolytes: Including electrolytes (especially sodium) in your fluid is important for a couple of reasons. First, sodium helps your body absorb water more effectively and retain it, which is useful when you only get one chance to drinkprecisionhydration.com. Second, even though cold water blunts thirst, you might experience cold-induced diuresis – the body’s response to cold that makes you need to urinate more. Cold diuresis can lead to extra fluid loss and some electrolyte loss. A sports drink or electrolyte-added drink at your feed will counteract this by replenishing some sodium. In practice, simply use a standard sports drink (they are formulated with salts), or if using a homemade carb drink, add ~1/4 to 1/2 teaspoon of salt per liter. This will help ensure that when you drink, the fluid is retained and used.

• Monitor Intake: With only one on-course feed, you won’t have the luxury of frequent drinking, so focus on getting ~200-300 ml in at that stop. Post-swim, you can rehydrate fully. One advantage of the cold water is you’re at lower risk of severe dehydration than if it were hot; just don’t ignore your body’s signals. If your mouth is extremely dry or you feel lightheaded, it could indicate you need fluids (though in a single-feed swim, you’ll have to push through to the station). Typically, the plan of a decent pre-hydration and one mid-swim drink is sufficient for a ~3.5-hour cold water swim.

In summary, don’t neglect hydration because it’s cold – drink some at your feed to replace lost fluids. But you also don’t need to guzzle huge amounts; over-hydrating can be counterproductive. Balance is key.

Thermal Support and Cold-Water Considerations

Managing body heat is as important as managing energy in a 15°C swim. You want to minimize heat loss and keep your core temperature up so that your muscles stay effective and you remain comfortable. Here are recommendations for thermal support:

• Wetsuit vs. “Skins”: If the event rules allow a wetsuit (and you are not vehemently opposed to it), a well-fitted wetsuit is highly recommendedat 15°C, especially given your limited cold-water experience. A neoprene wetsuit (even a sleeveless or a thinner one if flexibility is a concern) will dramatically reduce heat loss by insulating you. This not only helps prevent hypothermia, but also means your body wastes less energy on staying warm (so more energy goes into swimming forward). Many organized 12 km swims in sub-16°C water encourage or require wetsuits for safety. If you choose to swim without a wetsuit (skin swimming), ensure you have done extensive cold-water acclimation. Non-wetsuit marathon swimmers often have higher body fat and experience in cold; if that’s not you, a wetsuit is the safer choice. That said, even with a wetsuit, 15°C water will feel chilly after a while, so the following measures help in both cases.

• Insulating Accessories: Pay special attention to your extremities and head. Wear a snug swim cap that retains heat – silicone caps are better than latex for warmth, and a neoprene cap is even warmerusms.org. In fact, many open water swimmers double up caps in cold water (for example, a silicone cap under a neoprene cap) for extra insulationusms.org. Keeping your head warm can make a big difference in how cold you feel overall. Ear plugs are another small but effective tool: by keeping cold water out of your ear canals, you can prevent that ice-water shock to your inner ear that makes you feel colder and can even cause disorientationusms.org. It’s been noted that just a few drops of cold water in the ear can trigger dizziness and make your whole body feelcolderusms.org, so plug up those ears (with silicone or wax earplugs) to preserve warmth and balance. For your body, if you’re in a wetsuit, you’re covered; if not, some swimmers apply a layer of grease (lanolin or Vaseline) on exposed skin. This won’t stop heat loss in any major way, but it can provide a slight buffer and reduce evaporative cooling and wind chill if it’s breezy, plus it helps prevent chafing.

• Warm Feeding: Use your feed stop as an opportunity not just to fuel, but to warm up internally. As mentioned, have your drink warmed if possibledarren-miller.com. Even a lukewarm sugary drink can feel very comforting in cold conditions. The warmth in your stomach can stave off shivers. Some swimmers even hold the cup/bottle for a few extra seconds to warm their hands before tossing it. Just the act of stopping and consuming calories will help your body generate heat (digesting carbohydrates can raise body heat slightly, and shivering will convert that fuel to warmth if you’re very cold).

• Keep Moving: Try to avoid long pauses. Constant movement generates heat. If you must stop (at the feed or if adjusting goggles), try to keep your legs kicking gently. In a wetsuit, you’ll retain heat better even if you stop, but in just a swimsuit you can get cold fast when stationary. After the feed, expect that you might feel a chill for a minute or two when you resume swimming – kick a bit harder to get your blood flowing and you’ll warm back up. If you find yourself excessively chilled while swimming, you can increase your effort slightly for a short period to produce more body heat (just be mindful of not exhausting yourself).

• Watch for Hypothermia Signs: Even with all these precautions, be mindful of how you feel. If you start to feel confused, or your stroke rate slows unintentionally, or you have uncontrollable shivering, those are danger signs in cold water. Usually, with a wetsuit and proper feeding, you’ll be fine for 3.5 hours at 15°C, but every individual is different. The feeding strategy actually ties in here: by keeping your energy levels up, you give your body fuel to heat itself. (Marathon swimmer Darren Miller noted he needed 800–900 calories per hour in the 16°C English Channel, as opposed to 600–700 in warmer water, because the cold demanded extra energy for heatingdarren-miller.com.) So fueling well is part of your thermal strategy.

In short, dress for the temperature (wetsuit and accessories as allowed), use your nutrition to aid warmth (warm drinks, ample calories), and don’t linger in the cold longer than necessary. This way, you’ll minimize the cold’s impact on your performance.

Maintaining Energy to the Finish

By following the above fueling plan, you put yourself in a good position to maintain energy throughout the 12 km. A few additional tips to ensure you finish strong:

• Pace and Energy Management: Start at a steady, sustainable pace so you don’t burn through your glycogen too quickly in the first half. If you go out too hard, you might exhaust your carbohydrate stores early, making the latter part of the swim very tough. Aim for an even or slightly negative split (slightly faster in second half if possible). Knowing you have that feed at 6 km, you can mentally break the race into two 6 km segments. The goal is to still have some “gas in the tank” when you arrive at the feed, then refuel and rely on that boost (plus your remaining reserves) to carry you through the last 6 km. If you’ve eaten and hydrated properly pre-race and at the feed, your body should have enough energy available to keep your arms turning over for the full distance.

• Caffeine and Mental Boost: If you included caffeine in your strategy (say, a caffeine gel at the feed or a caffeinated drink), you’ll likely feel its benefits in the final hour. Caffeine can heighten your alertness and reduce the perception of effort, which is very useful when fatigue sets inusms.org. Even if you didn’t take caffeine, the sugar from your feed should be kicking in to help you avoid any major energy bonk. Mentally, remind yourself that you’ve fueled well – sometimes just knowing “I took in what I needed, I’m good to go” can push you through moments of doubt.

• Body Warmth and Energy: As you continue, be aware that as long as you’re moving and you’ve kept fed, you’ll generate heat and maintain your core temperature. If you start feeling excessively cold in the final stretch, it’s a signal to pick up your pace a little if you can (the paradox of cold swims is that working a bit harder can actually help you finish, because the increased exertion warms you up and gives a final adrenaline kick). By the last couple kilometers, you can usually give whatever is left in the tank, knowing you’ll soon be able to exit and warm up. Many swimmers get a second wind in the final kilometer, spurred by the proximity of the finish.

• Post-Finish: While not part of the swim itself, plan to rapidly refuel and rewarm once you’re out. Have a warm drink and a carbohydrate + protein snack ready (even something like hot cocoa and a protein bar, or a recovery shake) to start replenishing energy and to help raise your body temperature. You’ll have used up a lot of glycogen, so a solid meal within 30–60 minutes after finishing will help your recoveryusms.org. Also, get into dry clothes and bundle up quickly – the real chills often hit after finishing when your body is exhausted, a condition known as “afterdrop.” Prevent that by getting warm and eating something. This post-swim plan doesn’t directly affect your performance during the swim, but it ensures you recover safely and feel better after such a long effort.

Conclusion

In summary, successfully completing a 12 km open water swim in cold 15°C water requires a well-thought-out feeding and hydration strategy tailored to the conditions. Start by fueling up before the swim – a carb-rich meal and snacks will stock your energy stores. During the swim, capitalize on your single 6 km feed: take in fast-absorbing carbs (a warm sports drink, energy gel, etc.) and some fluid to replenish both energy and hydration. Opt for easily consumed fuels (liquids and gels over solids) to minimize time spent stopped. Concurrently, mitigate the cold by wearing appropriate gear (wetsuit, insulating caps, ear plugs, etc.) and using your fuel to help keep you warm (warm drinks, adequate calories). All these measures work together to maintain your energy levelsacross the full 3.5 hours – keeping your muscles fueled and your core temperature up. With practiced feeding techniques and good pacing, you’ll avoid the dreaded bonk, stay as comfortable as possible in the chilly water, and be able to finish the 12 km swim strong. Good luck, and enjoy the challenge!