Can you swim for four hours straight? What about six hours? Ten hours? 20 hours? 

If you’re wondering why anyone would ever want to swim for that long, you’re not alone. But that’s the reality of marathon swimming, and distance addicts around the world keep coming back for more.

While the marathon is typically associated with running, marathon swimming is becoming a more popular way for the world’s craziest athletes to test their mental and physical endurance in some of the most dangerous conditions in the world.

Is swimming a marathon harder than running one? We’re going to settle the debate once and for all! 

What is a Marathon Swim?

A marathon swim isn’t a relaxing dip in the ocean. And it’s definitely not the same as a marathon run, especially where distance is concerned.

Sure, some crazy people might try to swim a full 26.2 miles, but according to the Olympics rules, a marathon swim is any swim in open water (that’s a lake, river or ocean) that’s longer than 10 kilometers, or 6.2 miles. 

Marathon swims can be as long as 30 miles. It just depends on where you’re swimming, and how crazy you are!

The First Marathon Swim

And distance swimmers have been crazy for almost 150 years…One of the first ever recorded marathon swims was in 1875, when Captain Matthew Web swam 33 kilometers across the English Channel in 21 hours and 40 minutes. Yes, that’s almost a full day of continuous swimming. 

It seems that Captain Webb started a trend. Since his first recorded swim, more than 4,000 people have swum the English Channel…and even more people have tried – and failed – to complete the English Channel and other marathon swims. 

Famous Marathon Swim Races

These days, there are thousands of marathon swims around the world, but perhaps the most famous is the Triple Crown of open water swimming: 

  • 33.3 kilometers or 21 miles across the English Channel
  • 32 kilometers or 20 miles across the Catalina Channel in California
  • 45 kilometers or 28 miles around Manhattan Island in New York.

But those aren’t the only famous marathon swims by any means. There’s also the Oceans Seven, a brutal gauntlet of seven swims that takes swimmers on a globe trotting journey around the world, from 44 kilometers or 27 miles across the Moloka’i Channel in Hawaii to the North Channel, which stretches 34 kilometers, or 24 miles, between Ireland and Scotland. Plus five more intense swims in between.

10 Reasons a Runner Couldn’t Swim a Marathon

It’s clear that there are quite a few parallels between marathon swimming and marathon running. They both require a lot of training and mental strength, and an insane amount of endurance. But a few key things set marathon swimming apart as the clear winner. 

1. Running & Swimming Technique are Very Different

First of all, running technique doesn’t transfer well to swimming, and I’ll bet you a pretty penny that most elite runners would struggle to finish a 10k in a respectable time without any training. 

With months of intense swim workouts, a runner could probably do it, but being good at running doesn’t mean they’d be good at marathon swimming automatically. Sure, their cardiovascular fitness is on par with what’s needed for a marathon swim, but they won’t have the specialized technique that’s needed to swim efficiently for hours on end. 

Related: 5 Secrets to a Faster Open Water Swim Race

Swimming is a full-body sport that works your muscles in ways running just doesn’t match. And that’s partly why some runners use swimming as cross-training or injury rehab, which ends up making them better runners!

It’s also worth saying that swimmers aren’t always great runners, either. If you want to be good at doing something for a really long time, it’s going to take some specialized training. There’s no way around it!

2. Marathon Swimming is Lonely

Plus, marathon swimming can be really lonely. Most of the time, swimmers do solo marathon swims and end up trudging through rough conditions totally alone, with their support crew watching from a boat nearby. It’s easier to surround yourself with people during marathon runs, since the majority of the time you’ll be racing in a big group.

3. The Training is Intense

And don’t even get me started on the training. To prepare for a long marathon swim, you’re going to spend a ton of time in the water. Marathon swimmers who train alone end up spending hours staring at the black line on the bottom of the pool, or use their weekends to travel out to open water training spots. 

Related: How I Train for Marathon Open Water Swims

Depending on the length of their race, swimmers may log upwards of 20 to 30,000 meters per week or more. And since swimming typically takes longer than running, marathon swimmers end up training for more hours than runners, although that’s not always the case. And that doesn’t include out-of-the-water training, like strength workouts, recovery stretching, and more. 

If you’re new to marathon swimming and want to see if you can handle the training, check out the 10k Challenge or 10k Open Water Training Plans in the MySwimPro app. MySwimPro Coach will create a personalized plan based on your swimming speed that will whip you into shape for a 10,000 meter pool workout or your first 10k marathon swim in open water. The key to success in marathon swimming is consistency and following a progression, and these customized plans will help you get there!

4. Unsettling Environment

Swimmers have to do one thing that runners will never do: Look down into the mysterious abyss, with no idea what lies in the water beneath them. They might end up swimming through the night, with pitch black closing in from all sides, and minimal light to guide them as they go. And, somehow, they have to swim straight with no official course to guide them. Runners don’t have to worry about any of that!

5. Nasty Weather Conditions

Weather can also make or break a marathon swim. Currents, wind, sun, and waves often push swimmers over the edge. 

In the wrong conditions, a swimmer may end up swimming kilometers longer than planned, or they could overshoot their finish point due to strong currents and have to fight their way back. Sometimes the currents are so strong that a swimmer ends up adding multiple hours to their race time, or they might have to give up after losing their battle with mother nature.

There’s very little chance of that happening in an organized marathon run, where the course never moves.

Swimmers also put themselves at risk for hypothermia, since they’re spending hours and hours in the freezing cold water, many without a wetsuit. 

6. Wildlife Encounters

Plus, there’s the wildlife factor. Imagine getting stung by a swarm of bees and having to keep running. Crazy right? 

Related: 7 Stunning Open Water Swimming Destinations Around the World

Marathon swimmers often have to deal with jellyfish stings and other aquatic animal sightings during their swims. Many swimmers force themselves to power through hundreds of jellyfish to complete their races.

Maybe the threat of jellyfish stings would make you swim faster…who knows! 

7. Extra Long Race Times

Speaking of speed, marathon swims typically take much longer than marathon runs. 

In the Olympic Games, the 10k marathon swim takes the world’s fastest swimmers around two hours, which is about the same as the marathon run. 

But what about the rest of us? An average 10k could take four to six hours, but longer swims, like the 21-mile English Channel, take about 13 hours. And that’s just the average. Many swimmers finish much slower than that. 

To put it in perspective, the average marathon run time is about four and a half hours. Triple that, maybe add a few more hours, and that’s how long it takes to swim 26 miles.

8. Strict Rules

If we haven’t convinced you of marathon swimming’s superiority yet, let’s take a look at the rules. Official marathon swimming rules are super strict. 

According to the Marathon Swimmers Federation’s rules, swimmers can’t wear wetsuits or use gear that enhances buoyancy during their swims. And when you have to swim in water that can be freezing cold, swimming without a wetsuit is extremely tough. 

What if you had to run a marathon in the winter wearing just shorts and a t-shirt? That’s essentially what marathon swimmers have to do! It’s a massive challenge both mentally and physically, and it can be deadly if the swimmer isn’t prepared for it.

On average, the water in the North Channel, between Ireland and Scotland, is about 54 degrees Fahrenheit, or 12 degrees Celsius. At 21 miles, that’s a long swim to be without a wetsuit!

Swimmers also can’t make physical contact with anyone for the entirety of their race. So nutrition and hydration can be a challenge. Runners can stop at an aid station, catch their breath, maybe have a sip of water. It sounds so relaxing! 

But marathon swimmers? They have to tread water and stay afloat while they refuel, so it’s not really a break. Their support crew passes sports drinks, water, gels and other snacks to the swimmer, and they quickly grab what they need and get back to swimming as quickly as possible.

9. Weight Loss During Races

Speaking of nutrition, a lot of English Channel swimmers end up losing weight during their swim, and it’s not just water weight. 

Related: How to Swim Straight in Open Water

On average, a swimmer could expect to lose about four kilograms, or almost nine pounds, of bodyweight while swimming. No, this is not weight loss from training. This happens during their crossing.

Marathon runners might lose some water weight during a race, but their losses won’t approach anywhere near that extreme. In fact, many marathon swimmers actually bulk up and gain extra body fat during training, both to use as extra warmth and to account for weight loss mid-race.

10. It Burns More Calories

One more thing, since we’re talking weight loss. Let’s talk calorie burn. Swimming a marathon burns way more calories than running a marathon. 

Of course, calorie burn varies widely based on sex, age, body size and other factors. But according to the American College of Sports Medicine, a 155-pound person will burn about 493 calories swimming slow freestyle for an hour. By contrast, Harvard Health Publishing reports that a 155-pound person burns approximately 288 calories per hour when running at a 12-minute mile pace. 

A 12-minute mile results in a five hour, 14 minute marathon finish time, burning about 1,500 calories. Our swimmer, though, would burn 6,400 calories during a 13-hour English Channel crossing. A four-hour 10k swim would result in 1,900 calories burned. The proof is in the numbers!

Whether or not you think that marathon swimming is harder than marathon running, we can all agree on one thing: Marathon swimming isn’t for the faint of heart.

Let us know down in the comments if you would ever consider trying a marathon swim. Or if you have, let us know what your experience was like! And if you’re ready to start training, download the MySwimPro app for personalized workouts designed to help you conquer your first 10k!


1 Comment

  1. Robert Scammell on

    It is difficult to compare running and swimming. A 5 and a half hour marathon run can be achieved by a brisk walk and comparing it as a run with swimming is a stretch. 7 hour marathons are often achieved in Ironman Triathlons by non- runners with stops at every aid station and after a tiring 3.8km swim and 180km bike with drinking and eating at every aid station. It would be interesting to compare competitive marathon runners with similar swimmers. I have been around both and for a long tine generally observe that runners are leaner and I assume that is so because swimming is not a weight supported exercise . No floating in running just impact which results in better bone density but much more care has to be taken to ensure running longevity. Just the anecdotal opinion of a plus 30 competitive marathoner and a similar number of Ironman Tris and more research is required but so what I love both of them so they are both great for everyone (including walkers) to just get out there!

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