June 25, 2018

Swimming with the Garmin Forerunner 235

The Garmin Forerunner 235 is far from specifically designed for swimming, it is essentially a GPS running watch for outdoor use. However, a common new feature of most GPS watches these days is their waterproofing, in this case up to 50m. This means that it is perfectly protected to be used when swimming, or any other water based activity, meaning I gave it a try. I have also previously tried out the Garmin Vivosmart when swimming, but the results here were much more successful.

There is no specific swimming activity section like those seen in the triathlon watches and swim watches such as the Garmin Swim This meant that there would be no recording of specific ‘swim metrics’ data such as stroke rate and efficiency. Therefore, when using the 235 for swimming the best option would be the ‘other’ activity section. This can be used for any type of activity which is other than running and cycling – these are already pre programmed into the watch.

Pool Swimming

When swimming in open water, the watch can use the GPS capabilities and track your movement and distance. However, most likely, you will be swimming indoors in a lapped pool, therefore the GPS function will not work. As a result of this, the best option is to edit the data screens in the ‘Activity settings’ of the watch to display the number of laps (lengths) completed, alongside lap/ length time. This means that by knowing the length of the pool, the total elapsed distance would be easily calculated by also knowing the number of lengths you had done.

You can use the 'Other' Activity to take the 235 swimming
You can use the ‘Other’ Activity to take the 235 swimming

Each time a length is completed – in my case, 50m – the time for that length can be recorded by pressing the lap button. This is not the easiest manoeuvre as you have to break your stroke pattern to reach to your opposite wrist, however it doesn’t cause too many problems.

Open Water Swimming

Since initially writing this post, there has been a lot of good response on the open water swimming side. Since then, I have had some time to do some swims of my own where I have too been getting weird results regarding the distance tracking.

Garmin have a range of triathlon watches which are designed to be used in the sea of open lakes for outdoor swimming. The latest of these is the Forerunner 735XT which uses the internal accelerometer alongside the GPS to track stroke type in the specific Open Water Swim mode on the watch. This is different from the Forerunner 235 which has no Swim option, due to popular demand in the comments here is some extra information about the capabilities of the Forerunner 235 in open water.

When using the Forerunner 235 for open water swimming – or any other waterproofed GPS enabled watch for that matter – the main issue seen is inaccurate distances recorded whilst the route taken is often zig-zagging in nature and not in the straight path which the watch would always track on land.

Poor route tracking whilst open water swimming
Poor route tracking whilst open water swimming

This difference in GPS data when swimming is not due to the type of GPS hardware system (this is the same in all running and triathlon watches), but it is in fact a software based issue.

Garmin encode special algorithms for their triathlon watches for open water swimming where there are constant changes in GPS signal strength whilst the wrist is underwater. Therefore, these algorithms are capable of analysing and correcting for this when open water swimming.

The watch does work perfectly well in water however.
The watch does work perfectly well in water however.

This however is not written into the running specific (Forerunner 235) watches as they are not designed to be swam with. This is a shame as it makes the 235 not the best watch for swimming; yet it is understandable from Garmin’s standpoint as it separates their running and triathlon lines with these different capabilities.

One last quick tip to possibly try out when open water swimming would be to use a swim cap. The Forerunner 235 can be placed inside at the back of the cap (near the top of your neck) so that it is continuously near the surface whilst swimming. This will help avoid the losses in signal when the wrist is underwater.

This comes with some problems such as not being able to see any activity data in real time, however from personal use, this isn’t too key whilst swimming and also isn’t the easiest to view in mirkier water. Another consideration may also be the Forerunner falling out the back of the cap so make sure it is tightly fitted!

Another solution would be to swim in open water with a swim buoy which you can easily attach the watch to and would likely give much better results that when worn on the wrist.

ConnectiQ Apps

Since writing this post, I have been contacted by some developers of apps which allow the Garmin Forerunner 235 to be used as a swim watch. One app in particular I have seen to be quite popular is called ‘Pool Swim’ and can be downloaded via ConnectIQ here:

The ‘Pool Swim’ App is available to download to your device here.

Unfortunately I have yet had the opportunity to try out this app on my Forerunner 235, but will be doing so soon and updating this post to share the results.

Analysing Swim Data

When swimming indoors however, the watch won’t record or display your path which is a potential downside, yet again this isn’t a functionality which the watch is designed for. I found that the best thing to do (as previously said) is use the number of lengths and the pool length to calculate the distance covered and manually input this into Garmin Connect afterwards. There is an easy edit tool on the individual workout page where you can edit the time and distance covered.

Another thing to note, is that you can edit the activity type on Garmin Connect for that workout. When you download it, it will come up as an ‘Other’ activity, here you can change it to swimming and subsequently view all metrics in terms of pool length and pace (min/ 100m) which is useful.

For swimming in open water where the distance tracked is mostly inaccurate but not always too far adrift; you have the edit option for this too. Just click on edit activity when in Garmin Connect and the distance can be correctly altered to the known distance.

Knowing the correct distance swam is not always easy as veering off course whilst swimming is an often result. However, if competing in a triathlon (Olympic swim distance is 1500m) you would know your distance exactly. Another option would be to track the route you roughly swam via MapMyRun.com and then add this distance in manually afterwards.

Heart Rate Data

Lastly, the FR235 introduced a wrist based heart rate monitor meaning the need to wear a chest strap is no longer a necessity for heart rate data. Therefore, this would imply that heart rate data from swimming could also be recorded. However, the accuracy of this is to be questioned and I have no current means of testing the accuracy. For me, I found that the heart rate which was recorded was slightly higher than resting level with no major rise or fall seen.

Screen Shot 2016-02-11 at 16.18.56

It is also worth noting here that Garmin have newly introduced a sspecific swimming heart rate strap which can be worn in triathlons and paired with the triathlon watches. This would be a much more accurate means of recording heart rate than from the watch and would be interesting to compare the two results.



Overall, the Forerunner 235 has shown that despite not being designed for swimming, it is perfectly capable of meeting many of the needs which most amateur and recreational swimmers may want. Swimming in open water would give the best results, but if you want something which is waterproof and capable of giving you your length times, then the 235 is more than a good enough option. This also means that for the average person who goes to the gym, runs, cycles and occasionally swims, the Forerunner 235 is the perfect all round GPS watch.

Feel free to ask any questions – thanks for reading!


    • I’ve been using this app called Hoops Connect recently and it’s been great for finding fitness classes or sports sessions. I’m a runner myself and so it’s nice to be able to do it with other people rather than run on my own. I’ve even organised a few events myself and it went great! Here’s their website: http://hoopsapp.co My name on the app is Jordan Cambern if anyone wants to go for a run or try some other sport 🙂

  1. I use the Garmin 235 for outdoor swimming because I found this article.
    It’s a shame it does not work correctly, or is it just mine?
    The distance is way off, it records extra, I swam 3000 metres today and it recorded 2.93 miles, yes I probably zig zagged a bit but no way did I do it that much 🙂

    other than that it works great and very pleased with it.

    • I haven’t found this to happen just yet although I haven’t done too much pool swimming. I also now use the bright yellow band so any fading wouldn’t be as obvious.

  2. I’m using the 235 for 6 months now,for running, cycling and recently swimming. It s perfect for running and cycling with accurate data. Unfortunately for the open water the distances despite the GPS are far from accurate. It constantly adds about 500 meters every 1000 meters which is strange because in land is ok.

  3. Thank You great article. I tried to use the same method you mentioned in a swimming pool open. At the end each lap indicated weird distance as expected due to the gps.

    I am unable to adjust the distance of each lap back to 50m in the garmin connect. Or is this possible? Or I have not pre-set the other activities correctly.

    Looking forward for any advice.

    • In Garmin Connect you cannot alter specific lap distances, however, you can manually adjust the total distance/time of an activity. Therefore, as you are in a 50m lapped pool you know your individual lap distance (despite it not being displayed in Connect) along with each lap time, giving you a total time and distance which you can calculate and add on after.

      You can preset any activity to show different data fields or create a specific workout in Connect and then send it to your device. This is useful for timed intervals, but again will not work for indoor use for distances.

      I hope this has been helpful and don’t hesitate to ask if there are more questions.

    • Turn GPS off in the “other” mode and use the lap count times the pool length to get distance and add that at edit. Good estimate of time, distance, and hence pace.

  4. I read this article in hopes that it was just my watch, but unfortunately I have to agree with the other comments about inaccurate open water tracking…it’s pretty bad. Just did a 1200M swim and my FR235 read 1.43 miles (2300M). Cycling (with the cadence and speed sensors) and running has been great though.

  5. I use Forerunner 235 with application swimming prof. the Garmin store. The styles breaststroke swim, so I hand still under water. Therefore I give them to swimming goggles. So they do not measure heart rate, but the exact distance by GPS. But I would like to know whether the pair the watch with chest belt for swimming. Only to measure the pulse. Tri-HRM and HRM-swim. You do not have experience with it?

    • Yes, you are able to connect the FR325 to the Garmin HRM-Swim to measure heart rate when swimming. However, I do not have experience of this, but the consensus is that this is an effective way of measuring heart rate in water.

  6. Im an ex-pro swimmer and during summer times I do a lot of open water swimming races. I did a race over a strait (with accurate distance of 2300m, whereas my watch showed me 3080m). Later viewing on google maps it showed my trace as zick-zacking, going backwards and doing circles :D. Since there were heavy waves and the current was strong, Im thinking that when ever I hit my hand against a strong wave (disrupted freestyle) the GPS wont record a straight line. Does Garmin use a different GPS system on those triathlon watches, or how accurate is the GPS in open water there?? Regardless of the flaws in the GPS, the HR was quite good (u have to wear the watch quite tight, so there is less water disturbance between ur wrist and watch)

    I wish Garmin would come out with a better GPS thats capable in open water too 😉

    U can all view my track here (PS! please zoom in on google maps 😉 )

    • The problem that you – as with many others – are seeing with the recorded zig-zagging route and inaccurate distances is not due to the type of GPS hardware system (this is the same in all running and triathlon watches), but it is in fact a software based issue.

      Garmin encode special algorithms for their triathlon watches for open water swimming where there are constant changes in GPS signal strength whilst the wrist is underwater. Therefore, these algorithms are capable of analysing and correcting for this when open water swimming.

      This however is not written into the running specific (Forerunner 235) watches as they are not designed to be swam with. This is a shame as it makes the 235 not the best watch for swimming; yet it is understandable from Garmin’s standpoint as it separates their running and triathlon lines with these different capabilities. I hope this answers your question.

      • Thank You for the answer. I have another open water race coming up, but this time in calmer water. Im now curious how the watch is going to react there. But yes, I was aware that this isnt a pure swimmers watch. I love how accurate the 235 is on roads – either on foot or on bike (the main reason I bough it) 🙂

  7. Comgratulations. Very usefull information. Please, could you help me with a last information? About the pool length. In my case, my pool is 12,6 m (or 12 + 2/3). Can I insert this measure? (Or just aproximate? 12 or 12,5 or 13…for example). If not, the precision will be affected after 1 hour swimming. Understand my question? Thank you very much. Anderson.

    • Hi Anderson,

      It is possible to preset the watch to automatically lap after a set distance (in your case 12.6m – although the closest you can get to this is 0.05km). However, when using the match in a pool, you will be unable to connect to GPS to accurately track this. Therefore, what I would recommend is pressing the lap button each time you complete a lap and then afterwards you can edit the distance in Garmin Connect to display 12.6*(No. of laps) giving you your total distance.

      As the FR235 is not a swim specific watch, it is unable to calculate these laps for you and you will have to do it manually. I hope this answers your question.

  8. I’ve been swimming open water over the last summer with my forerunner 230 either in the swimcap or strapped to the lace of the goggles (on the back of my head). The accuracy improves significantly compared to that you get if you wear it on the wrist. You don’t get to check your metrics but I found I could rely on autolaps (set to 250m, the lowest possible) to know the distance I’ve swam. It may not be ideal but it’s good enough for me.

  9. Quick question. SO I have actually been afraid to use my forerunner 235 in the pool I don’t know I always think it will get totally messed up. If I purchase the strap will that help with getting data to see how many meters i’ve swam in a specific period of time? this might be a redundant question…(possibly dumb question) but nonetheless I want to know if I should purchase the strap at all.

    • If you’re talking about the heart rate strap, then no, it is not required to view your metrics (other than an accurate HR reading). The additional Heart Rate strap will only provide a more accurate measure of HR when you’re under water – the watch itself will no incur any damage from taking it under water at swimming depths .

Leave a Reply

Your email address will not be published.