Triathlon and Open water swimming are having a big moment in UK. With huge events like Ironman Leeds, the London T100, the Great North Swim and Swim Serpentine drawing record entries, more swimmers than ever are trading pool lanes for the thrill of lakes, rivers, docks, and coastal waters.
The real secret to feeling confident on race day? Training for the exact conditions you’ll face.
Open water swimming for triathlon is a completely different challenge to pool swimming. Depending on the location of your event, you could be dealing with cold water, wind, chop, limited visibility, and no lane lines to guide you.
In a race, you’ll also be surrounded by dozens (or hundreds) of other swimmers, all moving at once. The more you can train for triathlon open water swims in scenarios that match your race day, the better your swim will feel.
But before you swap every pool session for open water and jump in head first, there are a few things to think about...
What Should You Know Before Swimming in UK Lakes, Rivers, and Seas?
To kick off your training in open water, understanding your swim environment is super important to make sure you have a safe swim.
Temperature check: UK open water temperatures change dramatically through the year. Lakes can be as low as 4-6°C in winter, rise to around 10-12°C in spring, peak at roughly 15-20°C in high summer, and cool quickly again in autumn. Even in August, many inland spots stay on the cooler side compared to the sea. Acclimatise gradually at the start of the season, limit time in the water during colder months, and use thermal wetsuits or accessories like neoprene gloves and socks for year-round comfort.
Tides & currents: In coastal spots, learn tide times and how to spot and handle rip currents.
Venue quirks: Lakes can be dark, rivers can have currents, and docks require extra care - know exactly where the safe entry and exit points are, and check for slippery surfaces before you start your swim.
In a pool, the water is warm, flat, and predictable, with lane lines and walls to guide and rest against. In open water swims, you face different conditions.
You must sight to stay on course, pace yourself without walls, and adapt to the movement of other swimmers around you. These extra variables make open water both physically demanding and mentally more intense, which is why specific training is essential.
Open Water vs Pool Triathlon Swimming: Open water triathlon swims are harder than pool swims because they add cold water, waves, currents, sighting, and crowded starts to the challenge.
What To Wear For Open Water Swimming in the UK?
Wearing the right open water swimming kit can make the difference between an uncomfortable, short-lived dip and a confident, efficient swim. A good training swim will equal a better race day swim.
In UK conditions, where water temperatures are often cooler and visibility can vary compared to the beautiful waters in Europe, your kit needs to keep you warm, streamline your stroke, and help you navigate safely.
A good wetsuit, well-fitted goggles, and knowing what to wear underneath can boost performance. How? Having comfortable, warm kit and being able to see clearly can extend your time in the water, giving you more time in the water before event day.
Kit to consider:
Wetsuit: Most triathlons require you to wear a wetsuit. So don't leave it until race day to wear one, get used to how it feels during your training swims. A quality triathlon wetsuit boosts buoyancy and reduces drag. They keep you warmer than just a swimming costume or trisuit.
Goggles: A fresh pair of goggles allows you to see where you are going, sight buoys or landmarks and not vear off in the wrong direction - important for getting around the swim course on race day. Clear lenses are best for cloudy days, tinted or polarised lenses are best for bright sun.
Tri-suit or swimskin: Rather than always wearing your swimwear, practise swimming with your tri-suit under your wetsuit to make sure your swim stroke does not feel restricted and for a chance to practice your transitions. Think about investing in a swimskin for warm-water, non-wetsuit races.
How Can You Recreate Race-Day Conditions in Training?
Nothing quite matches the adrenaline and scenario of race day, but you can get close by building elements into your training.
The goal is to make event-day challenges feel familiar, so your body and mind know exactly what to do. So, to train for triathlon open water swims means practising starts in busy water, sighting buoys and swimming in different conditions. The more realistic your sessions, the calmer and faster you’ll be when it counts.
Simulating real race challenges will make the event feel familiar.
Group starts: Join a local tri club or swimming group and practice starting and swimming in small packs, this will give a feel of a mass start and having people around you in the water.
Sighting: Lift your eyes slightly every few strokes to find buoys in the distance, without breaking rhythm.
Choppy water: Train in breezy or wavy conditions to prepare for unpredictable race-day surfaces.
Wear your race day kit: Train in the exact wetsuit, goggles, and tri-suit you’ll use in the event. This helps you fine-tune the fit, spot any comfort issues (hello chafe-balm!), and get used to how your kit feels during the swim. Small things like if your goggles suction properly on your face, how your tri-suit fits under your wetsuit and how easily your wetsuit comes off can reduce stress on race day.
How Do You Stay Safe While Swimming in Open Water?
Open water swimming can be exhilarating, but can also be unpredictable. Water and weather conditions can change quickly, and even experienced swimmers can get caught out without the right safety habits.
Don't become complacent, no matter how often you swim in the same spot. No swim is worth risking your health or life for.
Follow these good safety habits during your training swims:
Never swim alone: Pair up with a friend or join a local club. Having someone nearby means help is at hand if anything goes wrong, and it also makes the swim more enjoyable.
Use a tow float: A bright tow float makes you far more visible to lifeguards, boaters, and other water users. It also gives you something to rest on if you get tired mid-swim.
Do a pre-swim check: Take a few minutes to scan the water before getting in. Look for SUP boarders and kayakers, boats, strong currents, floating debris, or sudden changes in weather. If something feels off, trust your instincts and skip the swim.
Know your limits: Open water has a way of exposing weaknesses in stamina and technique. Keep your first few swims shorter, and build up time and distance gradually.
Open Water Safety Checklist: Buddy swim, bright tow float, pre-swim water check, weather check, know your limits.
How Can You Track and Improve Your Open Water Swim Performance?
If your goal is to perform well in triathlon open water swims, tracking your progress is one of the smartest training habits you can build.
Race-day confidence doesn’t come just from swimming more, it comes from knowing exactly how your body responds to distance, temperature, and specific conditions, and using that knowledge to fine-tune your preparation.
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Use tech to guide your training: A GPS sports watch can track your distance, pace, stroke rate, and route, helping you replicate triathlon swim distances like 750m, 1.5km, or 3.8km
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Log your sessions: Record the location, water type (lake, river, sea), temperature, conditions, and your perceived effort. This builds a clear picture of how you handle the cooler, variable waters typical of UK triathlon events.
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Set clear race-focused goals: Train with your target event in mind - maybe that’s hitting a faster split for the Blenheim Palace Triathlon sprint distance, sustaining pace for the Great North Swim mile, or building endurance for the Ironman Leeds swim leg.
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Mix up your training: Include endurance swims for stamina, speed intervals for faster starts, and technique-focused drills to sharpen sighting in choppy water and swim streamlined to conserve energy for the bike.
- Review and adapt: Check your progress every few weeks. If you’re hitting your targets with ease, add more challenge. If you’re falling short, focus on recovery and technique before pushing distance.
Training for Triathlon Open Water Swimming in the UK
Pool swimming builds a base, but triathlon open water swims in the UK demand more: navigation skills, comfort in crowded starts, and the ability to stay efficient without lane lines or walls.
The athletes who thrive in events are the ones who’ve trained in conditions that match race day.
If you have got Blenheim Palace Triathlon in your calendar, add some lake swims to your training diary.
If you are taking on Ironman Swansea 70.3, be sure to head to the beach to practice swimming in the ocean.
You’ll be ready to tackle the swim with confidence, and still have energy left for the bike and run.
