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    > How can we improve the sustainability of long distance swimming as a sport?

    How can we improve the sustainability of long distance swimming as a sport?

    Open water swimming should be a relatively sustainable activity. How carbon-intensive could it be to move water with our body, after all? Yet, our sport comes with a host of training and safety gear, specific nutrition and a whole fitness ecosystem whose environmental impact is not negligible.

    While there’s no such thing as a free lunch, there’s also no such thing as an impact-free swim. Everything we do has an impact, but that impact can be reduced. By looking at the sustainability of our own open water swimming practices, we can find ways to do better, inspiring others to adopt a more sustainable approach.

    Let me guide you through my own swimming sustainability journey.

    Sun rising on the English Channel

    August 2023 – English Channel

    I am a long distance swimmer and I’ll take the following example to illustrate. When I emerged from the water at the end of my English Channel swim on August 23rd, 2023, after 19 hours and 16 minutes of swimming, I was shattered. Back on the support boat, I tried to fall asleep to the humming sound of the engine going full throttle back to Dover Harbour.

    There’s no denying it––for long distance swimmers, one-on-one support boats are a lifeline. However, these boats mostly run on marine diesel, a fossil fuel that contributes to global warming by emitting a combination of CO2 (carbon dioxide) and SOx (sulfur oxide). For any swimmer trying to improve their sustainability, that is an issue, but it’s not the only one––by far.

    What about flying to our next swim? Over the history of crossing the English Channel, 38% of crossings have been achieved by swimmers from the UK. The other 62% were overseas swimmers traveling from across the globe to face the Everest of swimming, with the flying CO2 emissions that it implies. The truth is, many long swims imply international flights or fossil fuel-powered support boats, both carbon-heavy modes of transportation. 

    Now, the idea is not to stop enjoying our sport altogether. However, there are certainly things we can do differently, so future generations can enjoy our passion too.

    While the following analysis focuses on distance swimming, arguably a niche audience, the same logic applies to triathlons, ironman, swim runs, swim holidays, or any sporting events with an open water swimming component––and that audience is massive and growing. If you are training for any swim, you will want to read this.

    Why Should We Care about the Sustainability of Open Water Swimming?

    Here is the contradiction: swimmers are famously fierce advocates for the seas and waterways. I’ve seen many swimming groups strongly advocate for plastic-free oceans, sewage-free rivers, or blue-green algae-free lakes. You would be hard-pressed to find people more committed to protecting marine biodiversity or fighting water pollution.

    Yet, our own lifestyle sometimes shows a cognitive disconnect when it comes to the bigger picture. Cheap flights make overseas swim events accessible at the click of a button, the cost factor trumping any environmental consequences. Would we do things differently if we had all the relevant insights?

    I wanted to research the direct and indirect environmental impacts of my own distance swimming activities, so I could look at ways to reduce my carbon footprint wherever possible.

    How to Measure The Sustainability of Swimming: Methodology

    To improve the sustainability of long distance swimming, I first needed to calculate its carbon footprint. Only by comparing quantifiable data could I draw conclusions and tackle the biggest priorities.

    In this article, I calculate the carbon footprint of an extreme sport challenge such as my own 2023 English Channel solo swim, putting figures on large posts such as transportation, food, energy and gear. To do so, I have adapted the methodology of carbon footprint calculators, such as the one offered by The Nature Conservancy, to my own swimming activities.

    Fortunately, I’ve been tracking my swimming activities in a spreadsheet (a bit old school) for the last year, and used this data to calculate my greenhouse gas (GHG) emissions. Down the line, this helped me identify the biggest sustainability issues and analyze the results, some of which you might find shocking (I know I did).

    Last, I looked at how to improve the sustainability of marathon or open water swimming in general, suggesting quick wins and longer-term goals. 

    Based on my data, carbon emissions related to open water swimming included: 

    • food eaten before/after, 
    • travel specifically for open water swimming, 
    • swim training in swimming pools and open water,
    • purchases of open water swimming items. 

    I did not include: 

    • cross-training activities, such as crossfit, cycling, pilates, or yoga,
    • physiotherapy to recover from injuries,
    • carbon emissions related to my “regular” lifestyle outside of swimming. 

    For the purposes of this exercise, I used GHG and CO2 interchangeably to cover all greenhouse gases, not just CO2. Last but not least, I focused on the incremental CO2 related to a single project over 12 months of training: my 2023 solo swim across the English Channel.

    Now that the ground rules are clear, it seems fair to start with a few swimming stats. 

    My English Channel Year in Stats 

    My English Channel year swimming stats are as follows: 

    • 532 km (330.6 miles) total swim distance 
    • 253 hours total swim time
    • Average swim distance 3 km (1.86 miles)
    • Average swim time 1 hour 25 minutes
    • Longest swim distance 40 km (24.8 miles)
    • Longest swim time 19 hours 16 minutes
    • 8 kg (17 lbs) body weight gain

    Carbon Emissions for my English Channel Year

    Carbon emissions (in kg CO2e)In percentage
    Food706 32%

    Note: this is just the 2208 kilos (2.21 metric tonnes) of carbon emitted for a single swim.

    Now for perspective, I want to give you an idea of how that compares to my overall carbon footprint, outside swimming. It’s hard to get a sense of what a ton of CO2 actually means, so here goes.

    English Channel Swim CO2 Emissions vs. Overall Non-Swimming Carbon Footprint

    Using the carbon footprint calculator of 2Tonnes, I found out that my carbon footprint for a year was 3.7 tCO2e. Therefore, the 2.21 tCO2e associated with my open water swimming activities represents 59% of my total carbon footprint for a year, and brings my total carbon footprint to 5.91 tCO2e.

    As you can see, this overwhelming proportion reflects the impact of a world-class swimming challenge.

    Let me break numbers down.

    Long Distance Swimming Sustainability: Transportation

    I’ll start with the big ticket item in any open water swim, transportation. I separated regular transportation (every weekday training) from exceptional transportation (swim camps abroad, weekends away by the sea, swim boat support). 

    Fortunately for regular week-day training, my carbon footprint is nil, as I cycle to all places and haven’t had a car since 2012. What I mean by “all places” is: my local swimming pool, the Serpentine in Hyde Park, my CrossFit gym, my physiotherapist, my pilates gym, and so forth. I literally use my bicycle for almost everything during the week.

    The issue lies with weekend training, swim camps and big swims, as they are further afield and require travel to the sea or the occasional lake outside London.

    Last year, I traveled overseas three times for my English Channel swim.

    1. Swim Camp in the South of France: Total Carbon Footprint 60 kg CO2e

    For that spring swim camp, I took the Eurostar train to Paris, then a high-speed train to Béziers where my father lives. I overnighted in Béziers, then drove to Palavas-les-Flots where the 2-day swim camp was taking place. 

    It looks like this:

    • A London to Paris Eurostar trip is 342 km (212 miles) and Eurostar trains emit 42g of CO2e per km (or 0.042 kg). Total for a round trip = 31.5kg CO2e.
    • A Paris to Béziers train trip is 804 km (500 miles) and SNCF trains emit 2.3g of CO2e per km. That’s crazy efficient. Total for a round trip = 3.7kg CO2e.
    • A Béziers to Palavas-les-Flots car trip is 65 km (40 miles) and an average car emits 192g of CO2e per km. Total for a round trip: 25kg CO2e.

    It’s kind of crazy to see how much more sustainable long train journeys are than a single short car journey.

    For comparison’s sake, had I opted to fly rather than take a train from London to Béziers, the total carbon footprint for this trip would have raised to 253 kg CO2e, as a round trip from London to Béziers by plane emits 228 kg CO2e per passenger for 1,960 km (1,218 miles).

    2. Swim Camp on a Greek Island: Total Carbon Footprint 624 kg CO2e 

    (10 times the amount of the France trip! Without even calculating emissions linked to boat support)

    This Greek swim camp was absolutely amazing and I loved every minute. As my friend Vanessa said, it made all the difference in my training. The carbon footprint, though, wasn’t so great.

    Underwater photo shows Laure Latham swimming around Mathraki in Greece, right arm in the pull phase of front crawl stroke

    I took a plane from London to the city of Corfu, then a bus from Corfu to the port of Agios Stefanos on the coast, then a motor boat from Agios Stefanos to Mathraki island. 

    The trip looks like this:

    • London – Corfu is 2,054km (1,276 miles) and I flew on an A320 aircraft (180-seater), which emits 140g of CO2e per passenger per km. Total for a round trip: 578 kg CO2e. Just to make it clear, it’s only for one passenger in economy class (business class passengers emit a lot more). For each trip, the plane emits at least 180 times that.
    • Corfu – Agios Stefanos is 28km (17 miles) and an average bus emits 822g per km. Total for a round trip: 46 kg CO2e.

    Keep in mind, however, that this calculation is incomplete because it does not include boat transports to and from the island. We went out twice a day for long swims escorted by big inflatable boats running on gasoline. 

    It’s exceptionally difficult to figure out the carbon footprint of boats when you have no idea about the efficiency of their engine and their average fuel consumption, or the influence of tides and winds. To me, that’s still a question mark as I struggle to quantify the carbon emissions of boat trips.

    3. Solo Swim across the English Channel: Total Carbon Footprint 454 kg CO2e

    I was very pleasantly surprised that the impact of a big swim with boat support was much lower than an international swim camp, and this will definitely help me make better swimming choices from now on. More on that later. 

    My crew and I drove to Dover Harbour, then from there hopped on a fishing boat, which was my support boat for the swim. 

    • The round trip to and from Dover by car emitted 45 kg CO2e.
    • The boat support emitted 409 kg CO2e.

    How did I get to this number for the boat? I’m lucky that my boat pilot was open to share his fuel consumption. This is a rough estimate at the top end of the range, as he said that each swim uses between 125 and 150 litres of marine diesel. The amount used depends on many factors, including tide, landing spot, swimmer’s pace, and most importantly, getting back to Dover. 

    According to a study by the International Maritime Organization, marine diesel oil emits 3,206 grams CO2 per gram of marine diesel oil. Since I got the total fuel usage in volume, I converted it to a weight unit. A litre of marine diesel weighs 0.85 kg. If my swim used up 150 litres of marine diesel (volume), that’s the equivalent of 127,5 kg of marine diesel (weight), then the total carbon emissions come up to 127.5 x 3.206 = 409 kg CO2e. 

    Note that I am a slow swimmer, which may impact the carbon emissions. On the lower end of the range (fast swimmer), the total emissions would drop to 340 kg CO2e, which is honestly, not bad at all for such an epic undertaking.

    4. Local Car Trips: Total Carbon Footprint 223 kg CO2e

    In addition to the above, I totaled slightly above 1,100 km of car trips from London to the coast to swim in the sea and to a couple of lakes, which came up to 223 kg CO2e. Not too shabby. 

    It would be great to be able to reduce that by taking the train, but for long sea swims, I needed to pack quite a lot of stuff, including nutrition, tow float, rewarming layers, sunscreen, etc. Also, trains are really expensive in the UK, so it’s not always an option financially.

    Long Distance Swimming Sustainability: Food

    Second largest post in my Channel swim’s sustainability audit, nutrition played a huge part of my English Channel training. I had to get it right to reach my goals. 

    As a rule of thumb, swimming burns 272 calories per hour and open water swimming in cold water burns 408 calories per hour. In order to replace all the calories burned during training and to put on 8 kg of body weight and fat, I ate 1.5 times my regular food intake during an entire year.

    Vegetarian Diet

    As I follow a mix of vegan and vegetarian diets, my regular food carbon footprint for a whole year is roughly 1.4 tCO2e (1,400 kg CO2e), which means the additional food I ate for the English Channel emitted 0.7 tCO2e. This was essential to prevent tissue damage, build my muscle mass and gain fat to manage hypothermia in cold water.

    Looking at my notes, I know that most of these calories came from carbs (fruits, bread, oatcakes, rice, pasta, potatoes), vegetables (lots of avocados), as well as oat products. However, the highest impact came from the proteins and fats I needed. I ate nuts (walnuts, almonds, hazelnuts) and dairy (mostly cream) on a daily basis and as much as I could, as I struggled to put on weight. 

    High Calorie Foods to Gain Weight

    In the case of nuts, I ate almond butter for breakfast and whole nuts later in the day as snacks. Dairy cream, well, I tried to sneak it in literally everything, which wasn’t always appetizing (tea with cream was a bad idea). Unfortunately, both nuts and dairy have a disproportionately high carbon impact for their nutritional value. 

    I had to supplement with a meal replacement powder called Complan, designed to help people gain weight. It’s a powdered drink that is high in calories, as well as vitamins and minerals.

    Sports Nutrition

    As far as “fuel” during swim sessions and the actual swim, I only used powdered maltodextrin (purified corn starch) and I didn’t consume any energy gels, energy bars or other common sport supplements. They’re not easy to digest during long swims. As powdered maltodextrin emits 1.7 CO2e per kg, and knowing I consumed about 8 kg of maltodextrin during the year, that only added 12 kg of CO2e.

    Hence, the carbon footprint associated with the extra food consumption was around 0.7 tCO2e.

    Moving on to energy.

    Long Distance Swimming Sustainability: Energy

    Home Energy

    In terms of energy, I did not heat our home more or take more showers while training. If I’m honest, it was quite the opposite. That 2022-2023 winter in the UK, energy prices went through the roof and as many others, I reduced the heating as much as was humanly tolerable for my two daughters. The upside was I needed to get used to being cold, so I “took one for the team” and willingly shivered, but my girls were cold that winter.

    Community Swimming Pool Energy

    Regarding swimming, my winter training took place at my local swimming pool, which is heated to 28C. The carbon footprint of heated swimming pools is 1 kg of CO2e per hour and I swam 103 hours in that pool, so that’s 103 kg of CO2e for a winter of pool training. That is actually ok. 

    If I was finicky, I would figure out the actual carbon footprint of using that particular pool, as it is on the ground floor of a hospital complex and uses the residual heat of the hospital to warm up the water. However, I’m afraid that’s frying my brain and I don’t have that data.  

    Last but not least, gear.

    Long Distance Swimming Sustainability: Gear

    I would be remiss if I didn’t look at the swimming gear I wore out in the course of training for my English Channel swim. At a glance, this includes swimming goggles, swimming paddles, swimsuits, ankle bands, tempo trainer, swimming earplugs, a swimming tow-float, glow sticks, LED necklaces, LED adventure lights, and several books on swimming, endurance and nutrition. 

    As can be guessed, a lot of swimming gear is made out of plastic or polyester, much of which comes from oil. 

    The thing is, with everything we buy, we never have any idea about any item’s carbon footprint. Was it manufactured in China and then shipped to Europe? Or, manufactured in the UK and trucked to a local logistics warehouse? And what about the polyester and plastic, the electronic components? 

    Good luck finding out the carbon footprint of each item:

    • It’s not on the companies’ websites.
    • It’s not in the product description. 
    • Nobody bothers listing the carbon footprint of millions and millions of products purchased every day in the world.

    I did contact each company, but haven’t had a single answer yet. By the way, the European Union will soon require thousands of large companies to actively identify and reduce human rights abuses and environmental damage in their supply chains. That means that in order to trade with the EU, any company will need to carry a sustainability audit of their supply chain. That is very exciting news.


    The swimming costume I used during my English Channel swim was manufactured by a German sports company called Slazenger. I contacted them about the carbon emissions related to the manufacturing of my swimsuit and their answer was most illuminating: “I will try to raise this inquiry with my management to seek counsel from their end and revert to you as soon as a reply is received from their end.” That was after eight emails. I never heard back. They have no idea.

    So, I’m afraid I must disappoint on that front. I have no clue about the sustainability of my swimming gear.

    Average Individual Carbon Emissions around the World

    As I mentioned earlier, my total carbon footprint for the year I trained for my Channel swim (swim excluded) was 3.7 tCO2e. With the swim, it increases to 5.91 tCo2e.

    How does 5.91 tonnes compare with average emissions from people around the world? (Note these are indicative averages for 2022 and vary hugely person to person).

    Europe (tCO2e per capita)Asia – Pacific (tCO2e per capita)America (tCO2e per capita)
    Denmark – 7.8Australia — 21.9Brazil — 6
    France – 6.5China – 10.9Canada — 19.8
    Germany – 9.4Indonesia – 4.4Mexico – 6
    UK – 6.2Japan – 9.4USA – 17.9

    If you are wondering why the average consumption in the UK is so much lower than Germany, I invite you to take a look at the study. Hint: it has to do with energy sources, renewables versus coal. 

    How Sustainable is Long Distance Swimming?

    Now that we’ve closed the loop, we’re back to the original question: what does the data say about the sustainability of open water swimming?

    For me, the answer is positive. If one makes conscious choices to limit carbon-intensive activities in the course of one’s life, there’s definitely room for extreme sports such as an English Channel swim.

    Analyzing the data, it turns out that travel constituted over half of my carbon emissions and contributed the biggest single environmental impact, followed closely by nutrition. A return plane trip to Corfu heavily tipped the balance of my transportation emissions. 

    So––what greener options can we choose?

    Sustainable Alternatives

    Swim Local If You Can

    If you are thinking of improving the sustainability of your open water and marathon swims, transportation is where you’re going to make the most difference. 

    • Opt for local swimming challenges where you can travel by train, bus or car. Forgoing planes is going to significantly reduce your swimming carbon emissions.
    • If, like me, you are bombarded with ads for cheap flights and if you can’t resist the appeal of big international swims––believe me, I get it––try to reduce the frequency of international swims that include plane travel. Say, if you usually do 2 or 3 international swims per year, try to reduce them to one a year or one every other year.
    • If you’re flying short-haul regionally for weekend swims or events, again, try to reduce the frequency of these events, or stay longer locally. The latter is not going to reduce your transport emissions, but at least you make worth your CO2.

    Cheap flights should come with a sustainability warning, much like cigarettes come with a health warning. They’re super damaging to the environment and should be seen as what they are.

    Prefer Plant-Based Foods 

    Nutrition can be a tough nut to crack, because we all have our established habits. Making your nutrition more sustainable is always achievable, though. 

    Cutting Down Meat: Resources for Athletes

    An easy one, if you eat meat every day, is to prefer plant-based meals at least once a week or more and eat less meat––particularly red meat. There are delicious plant-based recipes for all tastes.

    For inspiration, I invite you to check out Deliciously Ella where you can find easy and affordable plant-based recipes. I’ve got the No Meat Athlete cookbook and can definitely recommend it as a good resource in the kitchen.

    Try Dairy Alternatives

    More challenging but still feasible, removing dairy from a training diet would reduce its carbon emissions by 10 to 15%. I’m lucky that I love oat milk but if you don’t, there are plenty of plant alternatives, whether it’s rice, almond, hemp, coconut, soya or cashew based. You can also find delicious vegan cheese in most supermarkets.

    Become a Plant-Based Athlete

    At the top end of sustainability and if you feel that you can get all the nutrients you need for your swim challenges, go fully plant-based. A nutritionist might come in handy to help you get the right balance of everything. 

    I do know a few vegan Channel swimmers who had no issues completing the swim on a plant-based diet. None at all. One of my goals is to learn from them how they balance a vegan diet with the demands of marathon swimming. I also like baking cakes, so I guess I’ll have to experiment.

    Ask Questions

    Last but not least, I would urge you to ask questions about sustainability for all the swim events that you enter. 

    • Would it help you make a choice if you knew the carbon footprint of the swim for each swimmer? Ask for it.
    • Would it help you to know that a swim travel operator doesn’t fly all their staff for international trips and hires locals? Ask about it.
    • Would you like to know about swims that are accessible by public transport? Ask around.
    • Would you like more swims to be supported by kayaks, SUPs and electric boats rather than motor boats? Ask if it’s an option.
    • Would you like more affordable train or bus services where you live? Vote smartly at the next elections.

    Most importantly, enjoy swimming and good luck for your next swimming challenges!

    2 thoughts on “How can we improve the sustainability of long distance swimming as a sport?

    1. This is great! Thanks so much for opening our eyes to the carbon footprint of our choices. I’m not a swimmer, but I will certainly keep in mind the tenfold carbon cost of plane versus train-and pass this on to others!

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