We're now well into February, usually the coldest month for outdoor swimming, whether in fresh water or the sea, and that means things will soon be warming up again. Unless you've been one of the brave few taking to the water regularly throughout the winter, it is now time to plan your acclimatisation ahead of some exciting 2025 outdoor swimming.
Interesting factoid: did you know that 10 degrees Celsius isn't twice as warm as 5 degrees Celsius, but only 1.8% warmer in terms of the thermal energy contained in the water? It's very similar to why a size 10 shoe isn't twice as big as a size 5. That's because Celsius is an arbitrary scale based on two reference points: the freezing and boiling of water. A better scale for measuring small changes in water temperature is Fahrenheit, where 5C=41F and 10C=50F. Even Fahrenheit is an approximation though, albeit a better one that Celsius. IF you wanted to get really nerdy you'd use the Kelvin scale where zero Kelvin, sometimes known as Absolute Zero, is the point at which there is no thermal energy at all. Here's those temperatures once again: 5C=278K; and 10C=283K. If you want to follow the sea temperature (in Celsius) near Lymington there is an excellent live sea data buoy online here.
In 2025 we're delighted to introduce two Iconic Swims coaching courses led by Olympic Open Water medalist, Cassie Patten, at the Seawater Baths in Lymington, and also in the sea if the weather behaves. There is an Advanced course in June and an Intermediate course in July. For more info click here
By the time June comes around our stretch of the English Channel will have warmed up considerably from its chilly winter low, but at around 16 Celsius it is still cold compared to inland waters and this can sometimes catch people out. Late May and early June are often the times when there is the largest difference between the temperature of fresh water and that of the sea. Owing to its larger volume, the sea takes a long time to warm up and often doesn't reach peak warmth until late August, whereas your local lido, lake, reservoir or river - in the south of England at least - might climb from a chilly 5 to 20 Celsius by June, especially if we enjoy a warm spring.
This summer we are also running our acclaimed Thread The Needles swim days for the fifth consecutive year in July and August. You can either book one of the dates advertised or if you think you have enough swimmers for your own group of 8, do please get in touch and we'll organise your own private trip which should work out quite a bit cheaper per head. A word of caution: in 2024 we had a few swimmers join these swims who had not read the requirements and were disappointed when they found they were unable to attempt the swim because they could not swim well enough. If in doubt, please check first with us before booking. Watch this space as we will be running some free orientation swims in the spring where swimmers can find out about what it takes to Thread The Needles (or contact us for more info).
If you haven't practised any acclimatisation, an early summer dip in the sea, even on a lovely warm sunny day, can be quite a shock at 16 degrees. Going very carefully in the early days cannot be overstated as cold water shock can be deadly. However, once you've completed a couple of weeks of regular dipping - and even cold showers work - you should be fine for thirty minutes at a time in the water at that temperature. The trick is to keep moving. Just like when you run around on a cold day, your body will generate its own heat through exercise and stave off the shivers a little longer. Many consider a wetsuit when the water is that cold. If you decide to go down the wetsuit route, you should aim for a dedicated swimming wetsuit and, if possible, try it out beforehand. Common brands of swimming wetsuit include: Orca, Zone 3, Blue Seventy, & Huub. Swimming wetsuits are thinner around the shoulders and designed so you can turn your arms easily without chafing. One point worth noting though is that there are few wetsuits suitable for breaststroke - most are designed with front crawl in mind.
When planning your acclimatisation, look to begin in an open air unheated lido before moving on to a recognised open water lake venue. When preparing to swim the Channel I swam at Paliament Hill Fields Lido in London beginning in April before moving on to Shepperton Lake. To help you find your local venue NOWCA have published a useful list here. Always make sure when you first swim in open water there is a lifeguard on duty. Take great care if planning to plunge into your local river or lake. That is something to try later on, only once you are happy that you have built confidence in deep, cold water and should always be in a group and ideally with a swim guide who knows the area. When starting out, don't venture into the water until the temperature is in double figures, and try to go regularly as you'll find you acclimatise quickly over the course of the first few swims.
Here's an example acclimatisation programme for swimming without a wetsuit.
Week 1: 13 degree water, 10 minute swim;
Week 2: 14 degree water 15 minute swim;
Week 3: 15 degree water, 20 minute swim;
Week 4: 16 degree water, 25 minute swim.
There are several thermometers on the market which you can use to take the temperature of the water but your chosen venue should be able to tell you how cold the water is.
Watch out for air temperature too as the spring weather can sometimes catch you out with the occasional cold morning, even though the water is warmish. If wearing a wetsuit you can easily double those swim times but you should still start slowly. One last tip when starting out in a wetsuit is to deliberately fill your suit with water by gently pulling the collar of the suit open and dunking yourself to allow the water in. You get a bit of a shock at first but it is best to get that out of the way before you venture out into deeper water. If you do feel like you are ready to transition from wetsuit to skins, try taking your wetsuit off in the water at the end of a wetsuit swim and you'll find the water more bearable than going straight in without a suit for the first time.
Remember to take more layers of clothing than usual to put on after your swim, as well as a hot drink in a flask. As long as the air temperature is higher than the water temperature you should warm back up again soon enough, but you'll find wearing lots of warm clothing will help...and don't forget your woolly hat and gloves!
Once you've completed spring acclimatisation in your local lake, why not think about joining us for a sea swim or even for a whole weekend of south coast swimming. Here's a map of where we swim and here is a link to our swims
We look forward to swimming with you all in 2025!
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