Best Long Distance Open Water Swimming Events in and near London

Truth be told, I’m not a great swimmer. Don’t get me wrong, you could probably drop me a few miles off the sea shore on a stormy day, and I’ll find my way back without overly exhausting myself. I like to think that I’m a strong swimmer. The thing is, it will take me a very long time to swim back. I’m just so slow.


While I’m working on improving my technique and becoming faster, for the time being, the problem still persists. So I should mention upfront that I’ve not completed a lot of long-distance open water swimming events so far. Over the years, I did take part in quite a few.


At those events, at my swimming club, and elsewhere, I also spoke with a lot of long-distance open water swimmers and asked them about their experience. In addition to that, I did a fair bit of online research for this article, so hopefully you should be in safe hands here.

Feature photo (c) Runners World; from let to right, above, (c) David Hammant, Iain Weir, RaceCheck


Day, Date, approximate time: Sun 13 Aug 2023 at 7am

Where to be, approximately: Higginson Park, Marlow, SL7 2AE

Public transport: Need to arrive night before, book own accommodation. Marlow train station is 45mins (2 changes) or 1h (1 change) from London Paddington. From Marlow station, it is a 15min walk.

Distances: 13K, 5.5K

Cost: £160, £120, Early Bird & other discounts available

My favourite swim event by far has to be the Thames Marathon. Last year, it stretched over a distance of a whole 13km. Starting in Henley-on-Thames, it finishes in Marlow. Some of you might not be aware, but the Thames has next to no current on most days. When you watch leaves on the water, the direction of their travel is often solely determined by the wind, not by any current.


The river does not help you at all. If anything, the river tries to hold you back. So-called seaweed, which in many parts comes all the way to the surface in thick bunches, will slow you down through the friction it causes.


While I became a “DNF” (“did not finish”) due to severe muscle cramps in my calves after a few miles, I still have fond memories of the fabulous atmosphere. Some 800 swimmers turned the river into a white-water frenzy, while thousands cheered them on from the riverbanks. We had been really lucky with the warm, sunny weather as well. A half-marathon distance of 5.5km is also available and was chosen by many swimmers. In hindsight, that’s what I should have done, I’m not yet ready for the full distance.

Pictures above (c) Henley Swim, Tom J Powell, Henley Herald


Day, Date, approximate time: Sun 9 Jul 2023 at 6:15am

Where to be, approximately: The Loggia, near Hever Rd, Hever, Edenbridge TN8 7NG

Public transport: Need to arrive night before, book own accommodation. Hever train station is 40mins (0 changes) from London Bridge. From Hever station, it is a 30min walk.

Distances: 10K, 5K, 3.8K, 1.9K

Cost: £90, £65, £60, £50

My second most favourite swim is the Hever Castle Festival of Endurance. The castle and its surrounding parks are outrageously beautiful. Ellie & I have visited on various occasions. I’m registered again for the swim this year.


Each lap is 2km long and goes through the lake (which Hever Castle have simply labelled “The Lake” on their maps), then upriver around Thirteen Acre Island in the River Eden. There is next to no current, presumably because of the way the water is being directed right towards The Lake, before it enters the part of the river that goes around the Island. You could consider that part of the river to be a (particularly narrow, but still) part of the lake, if you like. Officially, it is the opposite way round. There is no lake and the wider bit of the river near the Island is just that: a wider part of River Eden.


The Festival of Endurance is a much bigger event than the Thames Marathon, including mostly triathlon races and other extreme stuff. This means that the atmosphere is not as suitable for amateurs and slower swimmers. Hever feels much more competitive than the Thames Marathon, even though the latter attracts much more world-class talent, I’m guessing. That said, it is a very friendly event, nonetheless. Everyone around you will be 100% focused, totally ‘in the zone’, and hell-bent on beating their personal best or breaking some record. But they will still be polite and won’t wish you any harm. Don’t expect any banter or casual chats, that’s all.

Pictures above (c) Henley Herald, SwimTayka, Bucks Free Press


The lake is incredibly shallow, perhaps on average 120cm deep or so, and the ground is rather muddy. In a way, this is good, because you will always be able to stand on the lake ground and your head will still be above the water. On the other hand, of course, your fingertips will sometimes touch the ground when you go about your business. You’ll also swallow some mud, when you accidentally swallow some water.


The river is on average a fair bit deeper, maybe 140cm, but there are shallower bits. The river bed is rocky, not muddy, with plenty of sharp root ends and submerged broken-off tree branches. Best not to get too close to the riverbank, stay with a group of experienced swimmers, and try to memorise which areas to avoid. The only issues when I took part, were not skewered swimmers or severed limbs. Instead, there were a couple of cases of hypothermia (including one wetsuit swimmer) and – in one case – an older participant feeling dizzy.


During the event I took part in, two years ago, the sky was so dark, it felt like middle of the night. We could see a couple of lightening strikes in the very, very far distance. It then rained real hard, like monsoon, for about an hour. All of us swimmers trusted the judgement of the seasoned race organisers. None of us were worried. If anything, we all felt that it was a pretty cool experience.


There are plenty of other Castle Race Series long distance open water swim events, including, for example, another splash at Hever Castle in September. Castle Race Series is mainly known for their triathlon events. However, nearly all of their triathlon events allow you to do only the swim or to enter separate swim events on the same weekend.

Just check their website for details. They are good at everything they do. I’ve booked running events through them, too, for example.

Pictures above (c) Outdoor Swimmer, Bucks Free Press, Leinster Express


Day, Date, approximate time: Sun 4 Jun 2023 at 6am

Where to be, approximately: Moyles Court School, Moyles Court, Ringwood, Hampshire, BH24 3NF

Public transport: Need to arrive night before, book own accommodation. Ellingham Crossroads is the nearest bus station. Take the train from London Waterloo to Bournemouth (1h45m, 0 changes), then the bus to Ellingham Crossroads (10mins walk to bus station, then 35mins on bus). From the bus station it is another 20mins walk, so you might be better off hiring a rental car (or using your own car), which is what I do.

Distances: 3.8K, 2.5K, 1.4K

Cost: £35, £33, £30

The New Forest Rattler is good fun. It comes in three distances: 3.8K (Epic), 2.5K (Standard), 1.4K (Half) and is set in a beautiful artificial lake. I enjoyed the fact that there were no more than perhaps another three dozen swimmers taking part, when I did, a few years ago. Almost felt like a family event or something. Kudos to the organisers, for getting this race so well organised despite the small number of participants. The communications won’t be as frequent and well-presented as with larger organisers, but in the end you’ll know when to be at which location.


Day, Date, approximate time: Sat 9 Sept 2023 at 8am

Where to be, approximately: Royal Victoria Dock, 1 Western Gateway, London E16 1XL

Distances: 15K, 10K, 5K, 3K, 1.5K

Cost: £122, £92, £67, £57, £30 to £42; Discounts for groups and NOWCA members available

London’s Dock2Dock is pretty cool and I’ve never heard of any issues with the water quality. Thousands of swimmers tackle a variety of distances. The entry requirements for the 15K are very high/difficult. In essence, you must have taken part in the Dock2Dock 15K in previous years, unless you’re extremely lucky to convince them otherwise.


Day, Date, approximate time: Sun 4 Jun 2023 at 9am

Where to be, approximately: Thames Valley Athletics Centre, Pococks Lane Eton, Windsor SL4 6HN

Public transport: Windsor & Eton Central Station is 40mins from London Paddington by train (1 change). Windsor & Eton Riverside Station is 55mins from London Waterloo (0 changes). There are further connections and routes. From either station it is about 25mins walk to registration.

Distance: 10K

Cost: £90

Jubilee River Swim (10K) is extremely well organised, scenic, and also has the huge advantage that the river has some current and is not almost stationary like the Thames.


Day, Date, approximate time: Sun 25 Jun 2023 (there’s another one in September) at 11:30am

Where to be, approximately: Eton College Rowing Centre, off Court Lane, Windsor SL4 6FJ

Public transport: You could do the same as for Jubilee River Swim, then walk the 40mins from either station to registration. However, it is at least 20mins quicker to take the train from London Paddington to Slough (13mins), then take the bus from there to Eton Wick (16mins) and walk the last stretch (20mins).

Distances: 10K, 5K, 3.8K, 2.5K

Cost: £50, £40, £34, £28

Especially the ‘long-distances’ (10K, 5K) at Swim Long Eton Dorney are getting rather repetitive, but good fun and decent value for money.


The good folk who organise the Thames Marathon, Henley Swim, also organise two further, award-winning, highly regarded long distance swim events: the Selkie Henley Classic (2.1K) and the famous Club-to-Pub (1.5K).


Day, Date, approximate time: Sun 25 Jun 2023 at 4am (sic!)

Where to be, approximately: Temple Island Meadows, Remenham Lane, Remenham, Henley-on-Thames RG9 3DB

Public transport: Take the train from London Paddington to Reading (25mins), then take the bus from there to Two Brewers bus stop (45mins), then walk from there (25mins).

Distances: 2.1K upstream (usually very little current)

Cost: £60

Link: here


Day, Date, approximate time: Sat 22 Jul 2023 at 6:45pm

Where to be, approximately: Henley Rowing Club, The Boat House, Wargrave Rd, Henley-on-Thames RG9 3JD

Public transport: Take the train from London Paddington to Twyford (40mins), then take the train from there to Henley-on-Thames (12mins). From there it will be a 15min walk.

Distances: 1.5K, partially upstream (usually very little current)

Cost: £59 (sold out this year except for charity entries)

Link: here


Day, Date, approximate time: [Seems to have been discontinued. Still popular with triathletes to practice swimming, though. Other activities, including swim events, sailing, etc.]

Where to be, approximately: Bewl Water Outdoor Centre, Bewlbridge Ln TN3 8JH

Public transport: n/a

Distances: 3.8K, 1.9K

Cost: n/a

The Bewl Triathlon Open Water Swim in Kent is 3.8K. A shorter 1.9K distance is available, too. When I took part, there were such strong winds that the waves were almost half a metre high (25cm above and below the water level) and breaking mid-lake all over the place, basically turning the race into a white-water event. Super-scary to a novice like me, but also kind of fun. Obviously this is not a regular feature of the course.


I also remember there being huge “No swimming” signs all along the lakeside with skull and bones symbols, that warned of half a dozen things that could kill or hurt you. Things like toxic blue-green algae, sharp-ended, underwater, metal obstructions, dangerous currents, underwater drains that could suck you in and turn you into a (not much longer) live plug, and so on. The race organisers came across as very professional. They told us, that everything was safe, and we felt reassured. Still, probably won’t do that one again.


If you made it all the way to the conclusion of this blog post, well done there. You’ve got the energy and persistence for long distance. Perhaps you are already an experienced long distance swimmer and were just looking for ideas of what other events you might have missed out on so far.

Should you be relatively new to the game, then I’d highly recommend, not emptying your bank account and booking a dozen swim events right away. Book one or two events and try to prepare properly for them. Don’t put yourself under pressure, but don’t give up either. Push yourself, stay with it, and I’m sure you’ll have a brilliant time.

To me, personally, those events are the highlights of the year. I cannot think of many activities better for the mind than long distance open water swimming.

Looking for another post about swimming? Check out my write-up about West Reservoir in North London. Other articles about outdoor activities include: running events in and near London, ocean rowing and hiking in Essex, rock-climbing in Wales, skiing in Bad Hofgastein, Motocross taster course near London, and caving in the Yorkshire Dales.

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  1. Pretty cool events here guys. I too can swim a little bit as far as distance but not for speed lol. It’s been such a long time as well but I know my wind is pretty strong. I bet you that seaweed can really hold you back.


  2. David was a competitive swimmer when he was young although these days it is purely recreational. I like the idea of a river swim but understand that the currents and stuff in the water would make it that much harder to swim. Never mind doing a long marathon swim. I am impressed that there are so many different swims in England. Good to help you to practice. I am not even sure I would go in the water. Says the woman who just completed the polar dip below the Antarctic Circle!

    1. How cool that David swam competitively as a young man, Linda. And even cooler that you guys have done the polar plunge. Antarctica is right up there on Ellie’s and my list. 🙂

  3. Swimming is my absolute favourite form of exercise – I just love it and can stay in the water all day. So it’s ironic that we live in the Midlands – about as far from the sea as you can get! It was really nice to read about these inland swimming events; places like Henley/Marlowe are eminently reachable. That said, while I love swimming, I’m slow and steady, so not good enough to compete in the really big challenges so it’s nice to know that there are a range of distances. Just getting out in the open water would be fab! And it’s lovely to hear about how friendly these events are.

    1. I had no idea you are a passionate swimmer, too, Mitch, how very cool! Would be awesome to bump into you (and Colin of course) at some of these swimming events. Do let me know in case you’re signing up for anything, if you like. I’d imagine you are a faster swimmer than me, I’m sometimes the slowest swimmer in the field haha… 🙂

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