Nutrition Strategies For Open Water Swimming


Stingray recently asked renewed sports nutritionist Marni Sumbal to give us her best advice for open water swim nutrition. She gives some great tips and guidance that can help all abilities.

There’s no question that open water swimming is an intimidating sport. Challenges include variable water temperatures, unpredictable water conditions, and unexpected sea life. While you may have your sights set on the grueling 21-mile English Channel swim, most open water swim events range from one-mile to 10K. No matter what swim distance you plan to complete on event day, there are a few nutritional suggestions to take into consideration in order to keep your training and racing experience safe, fun and performance-enhancing. 

Hydration and Fueling:

While it may not always be practical to take in fluids and calories as you are swimming, you do sweat in the water. When internal body temperature starts to rise (from exertion or water temperature), your body begins to sweat to prevent overheating. On dry land you can easily feel your sweat on your skin before it evaporates. But in the water, body heat transfers from your skin to the water so you’ll never feel yourself sweating. This can place you at risk for dehydration if fluids are not replaced during activities lasting longer than 90-minutes. Additionally, you may find yourself needing to urinate more often when swimming due to pressure changes that occur during water immersion. This can further dehydration.

Although short-distance swimming may not require the consumption of additional fluids and calories, failure to replace fluids, calories and electrolytes in workouts or events lasting longer than 90 minutes can compromise performance and health. Although the optimal feeding strategy is highly individual and involves swimmer preferences and the application of sound nutrition principles, here are a few tips to apply to your next workout or event:


It’s important to go into all physical activities well-hydrated and fueled. Carbohydrate ingestion before physical activity is designed to spare muscle glycogen, optimize blood glucose levels, boost motivation, delay fatigue and prevent hunger. Better hydration means better performance. Although lack of time, feeling rushed and body composition concerns are common excuses to skimp on (or skip) the pre-workout/event snack, there are clear performance advantages to your pre-competition fueling and hydration strategy.

To minimize the potential of upper or lower GI distress, prioritize low-fiber, energy dense carbohydrates with a little protein and/or fat. Depending on the time of the event/practice, allow:

  • 3-4 hours to digest a large meal (~450-800 calories)
  • 5-3 hours for a medium-sized meal (~250-450 calories)
  • 5-1.5 hours for a mini meal or snack (~100-250 calories)*
    *An ideal snack would include ~30-50g carbohydrates and ~5g protein/fat. An example would be one plain waffle + ½ tbsp nut butter + small banana.

Pre-workout fluid recommendations*: 

  • 16-20 ounce water at least 4 hours before activity.
  • 12-16 ounce water at least 2 hours before activity.
  • 8-12 ounce water ~10-20 min before activity.
    *Adding a small amount of sodium (salt) to a beverage may help simulate thirst and retain fluids. 1/8 tsp of salt = ~250mg of sodium.

During workout/Competition:

When it comes to performance, nutrition alone doesn’t limit performance but it can certainly affect how your body performs in a competitive setting. Consuming a sodium-rich sport drink can optimize hydration status during exercise. Additionally, proper fueling during exercise helps sustain a desirable effort and delay fatigue.

  • During pool workouts lasting more than 60-minutes, consume ~5 ounce fluid (1 ounce = 1 gulp), ~120-150mg sodium and ~10-20g carbohydrates every 10-15 minutes (or during rest intervals). Well-formulated sport drinks include Skratch, Clif, NBS, Infinit, Carborocket, Base and Nuun endurance.
  • During open water workouts and events lasting more than 60-minutes, consider using a feed zone (or returning to dry land) for regular consumption of a sport drink. Additional solid food (or gels/chews) can also be consumed every 30 minutes (wash down with water) for events lasting more than 90 minutes (if needed to delay hunger). Because a feed zone (or dry land) option may not always be available, make sure to always go into your event well hydrated and fueled.
  • In warm water/hot weather, choose cool, slightly sweet beverages.
  • For cold water/weather conditions, opt for more savory food options and hot drinks from a thermos may be preferred.
  • Vary flavors and textures to prevent taste bud fatigue. Compliment sweet sport drinks with savory food during long-duration events (ex. PB pretzel or rice balls).
  • You should feel comfortable grabbing fluids (ex. bottles) while moving (or during rest intervals) and drinking on a schedule in open water. To avoid losing momentum or to prevent getting cold, practice quick stops for food/fuel breaksAlthough solid and liquid forms of carbohydrate are equally effective during training and competition, you are encouraged to choose the fuel source that is most practical for the given workout duration, intensity, water conditions and training/event demands.

Post workout/Competition:

Falling short on recovery nutrition can place you at risk for sickness as intense or high volume activity can suppress the immune system. Although real food is generally encouraged over processed food, wholesome foods may not always be practical or feasible immediately after a workout or event. In many scenarios, a protein powder or meal replacement drink may be most advantageous. Begin consuming carbohydrates and protein immediately (or within 45 minutes) post-workout when blood flow to the muscles is elevated. To help with post workout refueling and rehydration, here are a few tips:

Short event (less than 60 minutes):

When: Within 30-60 minutes post workout (as tolerated)

What: Recover with a snack. Meal when ready.

How Much: Snack: 20-30 g protein + 40-60 g carbs.

Fluid Intake: 16-24 ounces

Moderate distance event (1-3 hours):

When: Within 30-60 minutes post workout (as tolerated)

What: Recover first with a snack. Meal when ready (within 2 hours post event)

How Much: Snack: 25-30 g protein + 60-90 g carbs. Meal: 20-30g protein, 60-90g carbs

Fluid Intake: 16-24 ounces in the 60 min post workout. Additional 16-24 ounce fluid in the next 90 minutes.

Long distance event (3-10+ hours):

When: Within 30-60 minutes post workout (as tolerated)

What: Recover first with a snack. Meal when ready (within 2 hours post event). If possible, eat another meal 3-4 hours after the event.

How Much: Snack: 25-30 g protein + 60-90 g carbs. Meal #1: 20-30g protein, 60-90g carbs. Meal #2: 20-30g protein, 60-90g carbs

Fluid Intake: ~16-24 ounces every 60-90 minutes for the next four hours.

Marni Sumbal, MS, RD, CSSD is a nationally recognized sports dietitian, author and triathlon coach. She is the author of Essential Sports Nutrition, The 365-day Running Journal and Athlete to Triathlete. Through her renowned successful private practice, Trimarni Coaching and Nutrition, she helps athletes from around the globe prepare physically and nutritionally for athletic events. As an elite endurance triathlete who has completed 16 Ironman-distance triathlons (including participating 5x in the Ironman World Championship in Kona, Hawaii) and placed overall female amateur at 2017 Ironman Chattanooga, she uses her real-life experiences and formal education to help educate, motivate and guide athletes to achieve athletic and nutritional excellence in training and on event day. Here unique "health first, performance second" approach of applying sports and daily nutrition science to real-world setting has gained popularity with many age-group and professional athletes who want practical and realistic nutrition and training strategies when preparing for athletic events. Marni frequently writes for Triathlete magazine, and and has been featured in Women's Running, the New York Times, Runner's World, Women's Health, Women's Running, Bicycling and Men's Journal. As a public speaker, she was also a regular guest in News4Jax in Jacksonville, Florida for live TV segments on nutrition. Marni lives near the mountains in Greenville, South Carolina with her husband Karel, and three four-legged kids: Campy, Madison, and Ella. You can contact Marni through her website,

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