How Do Open Water Swimmers Eat to Fuel Their Performance?

January 10, 2026 •

4 min read

A swimmer can burn over 1,000 calories per hour in cold open water, significantly higher than in a pool. This high-energy demand is why understanding how do open water swimmers eat and strategize their nutrition is crucial for success and endurance in long, challenging swims.

Quick Summary

Marathon and open water swimmers use a variety of strategies to fuel and hydrate during long events. This includes consuming liquid carbohydrates, gels, and select solid foods delivered via feeding stations or support boats to sustain energy levels and maintain peak performance.

Key Points

Pre-Swim Fueling: Carb-load in the days before a long swim and have a final, easily digestible meal 2-3 hours pre-race to maximize glycogen stores.
In-Water Nutrition: For swims over 90 minutes, consume liquid carbohydrates, energy gels, and chews every 30-60 minutes to maintain energy.
Efficient Feeding: Practice the 'Reach, Roll, Gulp, Go' technique with a feed stick and cup to minimize time spent stationary during feeding stops.
Balanced Hydration: Use electrolyte-enhanced sports drinks to replace sodium and other minerals lost through sweat, especially during long swims and in warm water.
Personalization is Key: Experiment with different foods and timings during training, never on race day, to find a nutrition strategy that works best for your body.
Warmth and Comfort: In cold water, opt for warm liquids like sports drinks or broth during feeds to help maintain core body temperature.

Mastering Nutrition for Open Water Success

Open water swimming presents unique nutritional challenges compared to pool swimming. Factors like varying water temperature, currents, and prolonged exertion demand a specialized and well-rehearsed fueling strategy. Proper nutrition is vital to prevent glycogen depletion, maintain hydration, and support mental fortitude during a long-distance effort. This involves careful planning before, during, and after a swim.

The All-Important Pre-Swim Preparation

Starting a long swim with a full energy tank is non-negotiable. The process begins days before the event.

Carbohydrate Loading

In the days leading up to a marathon swim, athletes engage in carbohydrate loading. This involves increasing carbohydrate intake to fill muscle glycogen stores, which serve as the body's primary fuel source during prolonged exercise. Focusing on easily digestible, low-fiber carbs is common to avoid an upset stomach.

The Race-Day Meal

On the day of the swim, a carb-rich, moderate-protein, low-fat breakfast is consumed 2-3 hours before the start. Popular options include porridge with fruit, toast with jam, or a bagel. A smaller, easily digestible snack, like an energy gel or banana, is often taken 30-60 minutes before getting into the water to top off energy stores.

Fueling During the Swim

For any swim lasting over 90 minutes, in-water fueling is necessary. Since chewing and swallowing can be difficult, most swimmers prioritize liquid and gel-based nutrition.

Liquid Feeds and Gels

Many marathon swimmers rely on a steady intake of liquid carbohydrates. These can be commercially available sports drinks or powdered maltodextrin mixes diluted in water. These are easily digestible and provide a consistent source of energy. Energy gels and chews are also a staple, offering a concentrated, quick hit of carbs. Gels are often washed down with a gulp of water to aid absorption.

Common In-Swim Nutrition Options:

Liquid Carbohydrates: Powdered drink mixes providing a steady stream of carbs and hydration.
Energy Gels: Convenient, concentrated packets of carbs for a quick boost.
Energy Chews: Gummy, candy-like blocks offering quick energy.
Bananas: Soft, easy-to-swallow fruit rich in carbohydrates and potassium.
Flattened Cola: A simple sugar boost for some swimmers.
Canned Peaches: Often used to combat seasickness and provide sugar.
Warm Broth: A popular choice in cold water for warmth and electrolytes.

The Feeding Process

In organized races or supported swims, nutrition is delivered by a coach from a kayak or boat using a feed stick with a cup or bottle. The World Open Water Swimming Association advocates an efficient four-step process: Reach and Roll, Gulp and Go. Swimmers aim to stop briefly, tread water, quickly consume their feed, and resume swimming to minimize momentum loss and heat loss.

The Importance of Hydration and Electrolytes

Despite being surrounded by water, dehydration is a risk for swimmers. Cold-water swimming can also trigger cold diuresis, increasing urination and fluid loss. Replenishing fluids and electrolytes is critical for performance and to prevent cramping.

Many swimmers use electrolyte-enhanced sports drinks to replace minerals lost through sweat, even in cooler water. In saltwater, while some sodium is ingested, it's not a reliable source of balanced electrolyte replacement. Some athletes use a preloading strategy with a high-sodium drink before a race to boost blood plasma volume.

Feeding Strategies: Liquids vs. Solids


Feature	Liquid Feeds (Drinks/Gels)	Solid Foods (Bananas, Bars, etc.)
Digestion Speed	Very fast; provides quick energy.	Slower; can cause stomach discomfort if not accustomed.
Convenience	Easy to swallow and consume with minimal effort.	Requires more chewing and time to ingest.
Energy Density	Concentrated source of carbohydrates.	Can offer a mix of carbs, protein, and fat.
Best Use	Continuous fueling during the main part of the swim.	Mental boost or variety for very long, multi-hour events.
Risk of Discomfort	Lower risk of digestive issues if practiced.	Higher risk of nausea or bloating, especially in rough water.

Post-Swim Recovery

As soon as the swim is finished, refueling with a combination of carbohydrates and protein is essential to replenish glycogen stores and aid muscle repair. A hot drink can also help raise core body temperature, especially after a cold swim. Common recovery options include smoothies, protein shakes, sandwiches, or a well-balanced meal. The “afterdrop” effect, where body temperature continues to fall post-swim, makes rapid refueling and rewarming a priority.

Conclusion

Eating during an open water swim is a precise, practiced art that requires careful planning and trial and error during training. Most swimmers prioritize easily digestible liquid and gel carbohydrates to maintain consistent energy levels, with feeding stations or support personnel delivering the nutrition. Hydration is key, regardless of water temperature, with electrolytes often incorporated into the fueling plan. By testing and refining a personal strategy, open water swimmers can ensure they have the fuel needed to overcome extreme distances and conditions. For additional training resources, check out the information provided by U.S. Masters Swimming.

Frequently Asked Questions

For marathon distances, swimmers typically aim for a feeding stop every 30 to 60 minutes to consistently replenish carbohydrates and fluids. The exact frequency depends on the individual's pace and tolerance.

Liquid carbohydrate mixes, energy gels, and chews are the most common. For solids, bananas are a popular choice due to their easy digestibility and high potassium content.

In organized events, food and drink are delivered by a support crew, often from a kayak or boat, using a long 'feed stick' with a cup or bottle attached. The swimmer briefly stops to grab the feed.

While some swimmers use small, soft solids like bananas or energy bar pieces for morale during very long swims, liquids and gels are generally preferred. Solids require more chewing and digestion, which can cause discomfort, especially in rough conditions.

Even though they are in water, swimmers sweat and lose fluids. Dehydration can impair performance. Maintaining electrolyte balance is also crucial, as minerals like sodium are lost through sweat.

Use insulated bottles to keep drinks warm, as cold liquid can be a shock to the system. Warm fluids can also help raise core temperature. Minimize time at the feed stop to avoid heat loss.

Yes, some endurance swimmers use a high-sodium electrolyte drink approximately 60-90 minutes before a swim. This practice, called 'preloading,' helps the body absorb and retain fluid, boosting hydration status.