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The Best Open Water Swimming Nutrition Guide

Congratulations you escaped lap swimming! Open-water swimming is exhilarating. However, venturing out into ocean, lake, and river swimming requires more planning since you can no longer reach for your nutrition on the pool deck. 

Read along to learn nutrition strategies for your open-water swim whether it be a race or a long training swim. We will teach you how to bring your fuel with you, how much to eat and drink before a workout or race and share easy tips that will optimize open-water swimmers’ performance.

The best open water swimming nutrtion guide by eatswim win.com with a photo of a swimmer swimming in the ocean in the background.

Carbohydrates are key 

Consuming enough carbohydrates before, during, and after an open water swim is the easiest way to enhance performance and reduce fatigue

Carbohydrates are in foods such as grains, fruits, legumes, dairy, sports drinks, and many more. When carbs are eaten the energy gets broken down and stored as glycogen in the liver and muscles. Your body breaks down glycogen for energy during exercise! 

Within 60-90 minutes of an open water swim all of your muscle glycogen gets broken down and used for energy. If you do not replenish with more carbohydrates the body breaks down fat and muscle for energy. (1)

Breaking down fat stores for energy is slow and less efficient so it may cause you to lose momentum and intensity during a workout or race. You also do not want to run out of muscle glycogen and have to rely on breaking down muscle for energy!

Carbohydrates help open-water swimmers maintain a high intensity and combat mental fatigue to win the distance! Nailing your open-water swimming nutrition plan begins with carbohydrates! Swimmers need food to fuel!

Fueling for the distance 

The further you swim, the more carbohydrates you will need per hour. Always practice using your fuel in training before a race!

How much carbohydrates do swimmers need? A graphic that shows sips of sports drinks for 30-60 minute long swim. 30 g of carb per hour for a 1-2 hour swim and 30-60 g carb for a 2-3 hour swim. For swims over 2.5 hours we recommend upwards of 60-90 g of carbohydrates per hour and a kayak escort to bring along fuel!

The following are carbohydrate recommendations during training (2): 

  • 30-60 minute swim: small amounts as needed 
  • 1-2 hour endurance swim: 30 g of carbohydrates per hour 
  • 2-3 hour endurance swim: 30-60 g of carbohydrates per hour
  • > 2.5-hour endurance swim: 60-90 g of carbohydrates per hour (adding small amounts of protein can also help to avoid gastrointestinal issues (GI)!) 

If you plan to compete in a long-distance swimming event lasting >3 hours we recommend connecting with an endurance sports dietitian to create an open-water swimming nutrition plan personalized to your needs. 

During swims, aim for low-fiber, low-fat carbohydrate foods for quick-digestible energy. Consuming a mixture of both glucose and fructose will help increase carbohydrate absorption, replenish glycogen stores more quickly, and help to prevent GI distress.

What to eat for a 1-3 hour long open water swim 

For a swim lasting longer than 1 hour bring at least 30 grams of carbohydrate fuel! If you are swimming for 2 hours aim for ~30 g of carbohydrates per hour. If you are planning to swim for over 2 hours aim for 30-60 g of carbohydrates per hour.

Here are examples of 30 g of carbohydrates you can tuck in your swimsuit (see our how-to video below):

  • 2-3 dates (remove the pit beforehand!) (~30-35 g carbs) 
  • 1/2 C boiled baby potatoes (~30 g carbs)
  • 1 large banana (~30 g carbs)
  • 1 C canned peaches in juice drained (~34 g carbs)
  • 1 pouch (10  pieces) of Skratch Labs energy chews (36 g carbs)
  • 4 Cliff Energy Blocks (32 g carbs)
  • Gu energy gel (~21-22 g of carbs) + sips of sports drink (~5-10 g carbs)
  • Honey stinger energy gel (24 g carbs) + sips of sports drink (5-10 g carbs)
Carbohydrate snacks to try while swimming: 
- banana
- dates
- gummy worms
- welches fruit snacks
- apple sauce
- sports gu's and gels
- raisins
- dried apples
- peaches
- larabar
- sports drink

What to do if I cannot tolerate fuel 

Open water swimming racing can be grueling! When the body is working hard this causes more blood flow to the muscles and away from the digestive tract. This can lead to stomach upset and an inability to take any carbohydrates without feeling sicker. 

If this occurs during training or a race try carbohydrate rinsing! You can chew up a gummy and let it sit in your mouth and spit it out. Or wash your mouth out with a sports drink containing carbohydrates and then spit it out (like a mouthwash!).

Research has found that carbohydrate rinsing may improve athletic performance by up to 2%! (3)

Hydration plan 

Hydration is key for preventing muscle cramps and fatigue to support optimal performance! Research has found that a 3% loss of body weight due to water loss significantly impairs performance. This is a loss of 4.5 lbs in a 150lb person. (4)

Open Water Swimming Hydration plan with a graph that encouraged 2-3 C of water 2-3 hours before training, 8oz of water 30 minutes before training, 16-24 oz of water during swim and 2C for every pound lost during the swim.

Here is the hydration plan we recommend:

  • 16-24 oz (2-3 C) of fluid 2-3 hours before training
  • 8 oz (1 C) of fluid 30 minutes before training
  • 16-24 oz (2-3 C) of fluid per hour 
  • Immediately after 16 oz (2 C) for each pound lost 

Check out our Sweat Rate Calculator! Sweat rates can vary anywhere from 1-4 lbs per hour of exercise. For each pound you lose, consume 2 C of water. 

The power of electrolytes 

Swimmers are notorious for not drinking enough water because they don’t feel like they are sweating. But, swimmers are sweating! Check out our blog post Do You Sweat When You Swim? For more details! Sweat leads to loss of fluid and electrolytes

Electrolytes are necessary for nerve function, muscle contraction, regulating blood pressure, balancing pH, and fluid balance. Sodium and chloride are the two main electrolytes lost through sweat. Smaller amounts of the electrolytes potassium, calcium, and magnesium are also lost via sweat. (5)

Some individuals are heavier, saltier sweaters! This can be determined through the use of a sweat patch. Check out our Ultimate Hydration Guide For Swimmers to learn more about picking electrolytes and sports drinks that meet your needs.

At a minimum, we recommend 250-500 mg of sodium every hour for races lasting >1 hour.

Adding salt to your pre-race beverage or meal may also help the body retain fluids during exercise. Try adding salty foods such as pretzels or salty peanut butter to your meals 3-4 hours before your race. 

You can also sip on sports drinks or add a pinch of salt to your water prior to racing! 

How to carry fuel during open-water swimming

It can be a challenge figuring out how to keep your fuel on you with minimal drag! 

Here is what we recommend:

  • Races under 60 minutes: you likely won’t need fuel, stash a gu or gels in your swimsuit just in case and prioritize pre-race hydration. 
  • Training and races 1-2 hours long: Carry a plastic water bottle tucked in your suit or a fold-up water bottle along with carbohydrate snacks such as gu’s, dates, or sports gummies 
  • Training > 2 hours long: Buy a flotation device and dry bag in one such as New Wave Swim Bubble that you can hook to your waist. This may add drag during training but will keep you visible to boaters and allow you to bring along more fuel. When in doubt, have a kayaker join you and carry your nutrition. 
  • Racing >2 hours: We recommend having a boat escort or kayaker come along to assist with your nutrition! It is important to keep in mind that dehydration and low blood sugar can be life-threatening. Nail your nutrition! 

Open water race day nutrition guide

Never try anything new on race day! Make sure that your open-water swimming nutrition plan has been practiced many times before your competition. The closer you get to the race or a training session the less protein, fat, and fiber you should consume.

Focus on simple carbohydrates as you get closer to your open-water swim. Try to eat a large meal 3-4 hours before your race and a pre-workout snack 1 hour before your race. Check out our blog What To Eat Before Swim Practice for snack ideas 60 minutes before racing!

How to calculate how many carbs you need

Take your body weight in pounds and divide it by 2.2 for kilograms.

Example: 150lbs/2.2 = 68 kg 

3 hours before your race 3g/kg body weight of carbs: 

EXAMPLE: 68 kg x 3 = 204 grams

2 hours before 2g/kg body weight of carbs:

EXAMPLE: 68 kg x 2= 136 grams

1 hour before 1 g/kg body weight of carbohydrates:

EXAMPLE: 68kg x 1= 68 grams 

Hourl goal for the race: 

30-60 g carbohydrates 


Be sure to practice your open-water nutrition before applying your fueling plan on race day! This can be done at masters swimming practice or the open water!

A fueled swimmer is a fast swimmer, try these open-water swimming nutrition tips!

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Ultimate Hydration Guide For Swimmers

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