Best Electrolytes for Swimmers: Yes, You Sweat in the Pool

By Sebastian Madlangbayan, founder of Cleonse: the world's cleanest 3-ingredient organic electrolyte.

Short answer: Yes, swimmers sweat, and that sweat carries salt. For a typical one-hour pool session, water is usually enough. Electrolytes earn their place for sessions longer than about 90 minutes, doubles, hot or humid pools, open-water racing and salty sweaters. Pick a drink with real sodium and a simple ingredient list.

Swimmers are the athletes most likely to tell me they don't need to hydrate. "I'm in water the whole time" sounds logical. But you're working hard inside a warm pool, often in a humid natatorium, and your body cools itself the same way it does on land: by sweating. You just don't notice it because the water rinses it off.

Do swimmers actually sweat?

They do. The best-known study on this followed 17 nationally ranked swimmers (male and female) through two intensive 105-minute training sessions. The air temperature in the pool hall was 36°C and the water was 27.4°C. The researchers, Maughan and colleagues, measured sweat with waterproof patches and tracked body weight, drinks and urine.

What they found:

• Average sweat loss was about 548 ml per session, a sweat rate of about 0.31 liters per hour.
• Sweat averaged 43 mmol/L sodium, 31 mmol/L chloride and 4 mmol/L potassium.
• Swimmers drank about 489 ml on average and finished essentially hydrated (about 0.1% body-weight loss).

So two honest takeaways. Swimmers sweat less than many land athletes during a normal pool session. And swimmers who sip from a bottle on the pool deck generally keep up just fine. That's the baseline, and it's why I don't think every swimmer needs an electrolyte drink every day.

Where swimming sweat gets serious

Things change once you leave the standard training session. A 2025 study of 45 elite open-water swimmers at an international competition (5 km and 10 km races) found average sweat rates of roughly 1.1 to 2.0 liters per hour, with the highest rates in warm water. That's in the same territory as land-based endurance athletes.

Setting	Average sweat rate	Source
Pool training, 105 min, national-level swimmers	~0.31 L/h	Maughan et al., 2009
Open-water racing, 5-10 km, elite	~1.1-2.0 L/h	Gonzalez-Custodio et al., 2025
Soccer (land comparison)	~0.94 L/h	Baker et al., 2019
Endurance sports (land comparison)	~1.28 L/h	Baker et al., 2019

The Baker 2019 numbers come from GSSI's normative sweat dataset of 1,303 athletes, and they show how much sweat varies by sport and by person. The point isn't that swimmers out-sweat runners. It's that the right answer depends on your session, your pool and your body.

Quick math: how much sodium a swimmer loses

Using the pool study's averages, here's a rough estimate. Sodium weighs about 23 mg per mmol, so 43 mmol/L of sweat works out to roughly 990 mg of sodium per liter.

• Typical pool session: 0.31 L/h × ~990 mg/L ≈ 300 mg of sodium per hour. Food easily covers that.
• Hard open-water race: 1.5 L/h × ~990 mg/L ≈ 1,500 mg of sodium per hour, if your sweat is as salty as the pool swimmers'. That adds up fast over a 10 km swim.

These are illustrations, not prescriptions. Sweat sodium can range from about 10 to 90 mmol/L between individuals, according to GSSI. A salty sweater could lose double the estimate. Someone else could lose half.

When swimmers should use electrolytes

The Gatorade Sports Science Institute's guidance on drinking strategies is useful here. Drinking to thirst tends to work for shorter sessions (under about 60-90 minutes), cooler conditions and lower intensity. A more planned approach makes sense for sessions longer than about 90 minutes, hot conditions, high intensity and high sweat rates. Losing 2% or more of your body weight to dehydration is where endurance performance starts to drop.

Translated for swimmers:

• Morning and evening doubles. Two sessions in a day add up, especially if you're not eating much in between.
• Long sets over 90 minutes. Distance swimmers and masters groups often hit this.
• Hot, humid natatoriums. The pool in that study had 36°C air. Plenty of indoor pools feel like a sauna.
• Open-water swims and triathlons. Longer efforts, sun exposure and fewer chances to drink.
• Salty sweaters. If you see salt marks on your cap or goggle strap after drying off, or you crave salty food after practice, pay attention.
• Swim meets. Long days on deck, warm-ups and multiple races.

For a regular 45-60 minute workout, plain water and a normal meal afterward is fine. I'd rather tell you that than sell you something you don't need.

What to look for in a swimmer's electrolyte

Sodium first. It's the main electrolyte in sweat by a wide margin. In that swimmer study, sweat had roughly ten times more sodium than potassium. Drinks that lead with potassium and go light on sodium are built backwards for sweat replacement.

A little carbohydrate for long sessions. Some sugar helps your gut absorb sodium and water, and it gives you fuel during long sets and meets. For short sessions you don't need much. For a 2-hour practice, it helps.

An easy stomach. Swimming is horizontal, high-effort and full of flip turns. Heavy, syrupy drinks or sugar alcohols can sit badly. Simple formulas tend to go down easier.

A short ingredient list. Swimmers often train twice a day, six days a week. If you drink something daily, it's worth knowing what's in it. Skip artificial sweeteners, dyes and gums when you can.

How Cleonse fits a swim bag

I built Cleonse around exactly those priorities. Three ingredients: organic lemon or strawberry powder, organic cane sugar and French grey sea salt. Each 30g stick has 500mg of sodium, 26g of carbohydrate and 100 calories, with 85+ trace minerals from the sea salt in trace amounts. No stevia, no artificial sweeteners, flavors or dyes, no gums or fillers. Every number is on the facts page.

Mixed into 16 oz of water, one stick of Cleonse comes out to about 46 mmol/L of sodium. That's right in line with the 43 mmol/L average sweat sodium in the swimmer study, so it's a sensible match for what you're actually losing. The carb concentration lands around 5.5%, which is in the range most sports drinks use for easy absorption.

How I'd use it:

• Long practice or doubles: one bottle on deck, sipped between sets.
• Open-water or triathlon training: one bottle before, and another after if it's hot or long.
• Meet days: sip through the day between events, alongside water and real food.
• Short, easy swims: just water.

If you want to know why I care so much about the ingredient list, I wrote about what makes an electrolyte truly clean.

Practical hydration habits for swimmers

• Keep a bottle at the end of your lane. The pool study showed swimmers stay hydrated when a drink is within reach.
• Weigh yourself before and after a long session once or twice. Each kilogram lost is roughly a liter of sweat. That tells you your personal sweat rate better than any chart.
• Don't overdrink. Drinking far more than you sweat dilutes your blood sodium. You shouldn't finish practice heavier than you started.
• Eat after practice. A salty, carb-rich meal does a lot of the recovery work on its own.
• Check your urine. Pale yellow is the goal. Dark and scant means you're behind.

For a big swim, a bottle of Cleonse on deck plus water is a simple system that covers sodium without a long list of additives.

FAQ

Do swimmers sweat in the pool?

Yes. In a study of 17 nationally ranked swimmers during 105-minute sessions, sweat rate averaged about 0.31 liters per hour, and sweat contained about 43 mmol/L of sodium. You don't notice it because the water washes it away.

Do swimmers need electrolytes or just water?

For a typical session under an hour, water is usually enough. Electrolytes help for sessions longer than about 90 minutes, doubles, hot or humid pools, open-water swims, meets and heavy or salty sweaters.

How much sodium do swimmers lose?

It varies widely. At the pool study's averages, roughly 300 mg per hour. In hard open-water racing, where sweat rates can reach 1-2 liters per hour, losses can climb above 1,000 mg per hour, depending on how salty your sweat is.

Should I drink electrolytes before or after swimming?

Both can work. For long or hot sessions, sip during practice from a bottle on deck. After a hard or long swim, an electrolyte drink plus a salty meal helps you rehydrate.

What's the best electrolyte drink for swimmers?

Look for meaningful sodium, a little carbohydrate for long sets and a short, clean ingredient list that sits easily in your stomach. Cleonse has 500mg sodium from French grey sea salt and three organic ingredients.

Keep reading

• How much sodium do athletes need?
• Electrolytes for muscle cramps: what actually helps
• Best electrolytes for cyclists

Editor's note: This article is for general education and isn't medical advice. Sources: Maughan RJ, Dargavel LA, Hares R, Shirreffs SM, "Water and salt balance of well-trained swimmers in training," Int J Sport Nutr Exerc Metab, 2009 (PubMed 20175429); Gonzalez-Custodio A et al., "Sweat rates during international open water competitions and the importance of feedings in elite swimmers," 2025; Baker LB et al., "Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: An update and analysis by sport," Journal of Sports Sciences, 2019 (via GSSI); Gatorade Sports Science Institute, "Sweat Biomarkers for Sports Science Applications" (sweat sodium 10-90 mmol/L); Kenefick RW, "Fluid Intake Strategies for Optimal Hydration & Performance: Planned Drinking vs. Drinking to Thirst," GSSI Sports Science Exchange #182, 2018. Sodium-per-hour figures are our illustrative calculations from published averages. Cleonse product facts are from our label.