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Fenix 6s Open Water Swimming under reporting distance & pace

Former Member
Former Member

I've upgraded to the Fenix 6s sapphire and the distance (and thus pace) is being under calculated on open water swimming. At first I thought I was just having a slow day or the current was stronger than usual but over multiple attempts I am getting the same result.

I have swam in the same bay for years and from my previous watch, triathlon times  and pool pace I know I average between 1:50 and 2:00 per 100m yet on the Garmin 6s it is showing more like 2:30m per 100m. 

I wore my friends Fenix 5 on one wrist with the 6 on the other and over a 600m swim the 6s reports 500m. Likewise over an Olympic triathlon distance swim (1800m) the 6s shows closer to 1500m. 

I have switched between glonass / galileo and changed GPS to every second to no avail. It seems to be more an error in the distance calculation rather than the GPS tracking as the route shows as accurate when looking at the  map post swim. Worth noting distance and pace is accurate for running and cycling. 

Has anyone else experienced this?  

  • 0 in reply to Olu.F.

    FR735XT is not secure waterproof (did a button-repair myself) And glued the glass. But Will do a swim tomorrow with both watches in the buoy

  • 0 in reply to Olu.F.

    i actually think that mine works better when i breathe in the opposite side that my watch is on.  i think that for me that's when the watch face the sky better. i noticed that if i breathe to the left and wear the watch on the left my watch is more perpendicular to the sky vs parallel to the sky. never had issues with other garmin watches so this may just be a marginal issue with gps on the f6. next time i will try to rotate my arm more to try to keep the watch parallel to the sky

  • 0 in reply to rene.brons

    Did an open water swim today: FR735XT And Fenix6 in my buoy: FR735XT: 5427 mtr

              Fenix: 5070 mtr

    Not as bad when wear the Fenix On my wrist but stil way to much off. And common I want this On my wrist. 
    I e-mailed Garmin support. Now wait 

  • 0 in reply to rene.brons

    The more people complain the sooner there will be response. I had a 2800m swim. The watch just showed 2100m. If you measure with Google Maps or do a correction with strava you get the 2800. if I open the fit file on https://www.fitfileviewer.com there are enough good GPS coordinates to measure the correct distance. Just try an xy-plot of the gps coordinates with excel. There are however some points missing. And that seems to be the source for the evil. Garmin has some algorithm that tries to estimate distance when GPS is temporarily lost. And they do not make a linear correction when GPS is back again. From support I only got the typical bla bla like put the watch under your bathing cap or into your bouy and so on. I insisted that they forward my analysis to development. They promised to do so. We will seeing there is a correction. For the F5 it took 3 years until OWS worked. I thought they learnt something with F6. I like the F6 nevertheless. However OWS should work better. And my recorded GPS data say they could do better!

  • 0 in reply to denglerfranz

    A couple of questions. I wanted to try to site you referenced fitfileviewer but I am not sure how to convert my swim to FIT. It seems that I can export it to a GPX or TCX but not FIT. I thought if I saved it as a course I would get the FIT file but it appears that for OWS activities, the option to save as course is not there. On my watch it appears like it doesnt get enough GPS points but the only way I can tell that is from the straight lines it draws from one point to the other.  Btw, I also read DCR review on the 945 (which uses the same GPS chipset and people there also complain about swim accuracy) and even Ray says on one of  his blogs (eqip I use for swim run bike) that he uses the 945 but he is still having swim accuracy issues.  I don't know how old that blog is but he also says that Garmin hopes to have it fixed in the summer. I just dont know if its this summer or last summer.  At any rate, if you can let me know how to convert my OWS activity to FIT I would like to try the site to see how the GPS points look.  I would say (other than my new battery consumption issue) the OWS is my only real issue with this watch.  Basically unusable for me as it.

  • 0

    I can confirm 3.8km Ironman open water swim... and my 6S Sapphire measured 3.2km total. I lost time debating if I had to do another lap or something (didn't). My sighting sucks and I would have swam MORE, not 600m less lol (more like 300m more).

  • 0 in reply to avikoren1

    Select to export original from Garmin Connect online.

  • 0 in reply to denglerfranz

    Well, thanks for that link.  This proves my suspicion that for the most part I dont have good GPS for a vast majority of my swim. This was shown as dashes for about half of my swim. What the watch does (just on first examination) is if it starts off with GPS it captures your speed as meters/sec.  Than if it loses GPS signal it continues with the last known speed and adjusts that speed up or down based on cadence, ie cadence goes up, than speed as a small up tick, etc.  It does a half way decent job at that.  But than, once GPS is returned (maybe its a poor signal) but on my file (and experience) it starts to generate speeds that are not possible for many ,many samples. So after losing GPS, say it continues with 1 meter/sec and slight adjustments based on my cadence. After it picks up GPS signal again, now the file shows 30 meters/sec for many seconds.  In my case this is why I end up with much longer distances on my activity vs the actual distance.  

  • 0 in reply to avikoren1

    As you are well aware, I am one of those for whom the OWS activity generally works on the watches I have swum with over the years (although don't ask me about OWS with my Marq Athlete. I still have a 3sec 250m after that played catch-up when I stopped at a buoy!). As a result I've not seen fit to analyze the data. However, lack of GPS is obviously the prime cause for the errors but the difficulty is in identifying the reason for that. I'm not a fast swimmer in the sea as is obvious and have a stroke turnover around 30 but my arm/wrist does come clear of the water between each stroke. 

    I do not believe there is generally a problem with the hardware although of course defective watches exist. The problem is likely a combination of the swimming style and the algorithm Garmin use to estimate swimming pace and distance. This has changed much over the years; the 935 was horrible when it first came out. Even now, occasional software changes throw a spanner in the works but in my experience these glitches are quickly fixed.

    For those people who have problems with OWS. I can only suggest you keep talking with Garmin. Hopefully, anything that makes your swimming results better does not negatively impact on mine and those others for whom it works Innocent