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Fenix 6s Open Water Swimming under reporting distance & pace

Sydney Ryan
over 4 years ago

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 over 4 years ago

    I've been finding things work exceptionally well with OWS on my Fenix 6X Solar; a couple of recent examples https://connect.garmin.com/modern/activity/5090578730 and https://connect.garmin.com/modern/activity/5123112769.  If you think the track accuracy of your 6s is good, then it may be that it is actually giving you the right distances and pace (and other watches are wrong); it's difficult to tell without you posting the activity with a scale to measure against.  That said, it is odd that the pace you are getting is so much slower than you know you do in the pool.

    If the track accuracy is good, but it's incorrectly calculating distance (and therefore pace), it may be the swim dead reckoning that's messed up (see the changes made from 5.00 to 6.00 here https://www8.garmin.com/support/download_details.jsp?id=15031 ).  As I understand it, swim dead reckoning is a bit like the how the watch calculates indoor running speed and distance from internal accelerometers; which requires some outdoor runs at different paces to get dialled in (see page 3 here http://static.garmin.com/pumac/fenix_6_6S_6X_Pro_OM_EN-US.pdf).  Years back, the Garmin devs that would occasionally drop in on these forums referred to the indoor running calculations as 'wrist dead reckoning' (or WDR);  hence, I'm pretty sure swim dead reckoning is a similar feature.  The point of swim dead reckoning is to help the watch to accrue distance and record pace during OWS, when GPS signal is lost temporarily or GPS is just poor (which can happen in lakes surrounded by steep cliffs).  Swim dead reckoning must rely on some sort of internal calibration factor; calculated after a few swims with good GPS.  It could be that factor didn't get calculated properly on your watch (if you've done a few OWS now), which means you could see if it improves after a few more swims (the watch corrects the internally recorded factor) or try a master reset (Menu>System>Reset>Delete Data and Reset Settings) to clear the internally stored factor and make the watch calculate a new one.  [The master reset does mean you have to spend a while reconfiguring the watch again after, so I'd suggest seeing if it improves after a few more OWS activities first.]

  • 0 over 4 years ago

    Like Crispin I've been having very few issues with my F6 Pro Sapphire swimming through the recent New Zealand summer. I swim a 2000m out and back buoyed course and find the distance and track accuracy good. 

    Pace in the sea can vary considerably compared to the pool particularly if the sea state is rough. Also, overall pace takes into account any stops.

    How is the swim course measured? I thought Oly distance swim was 1500m?

    Do you stop during your swim?

    Would you post a link to a swim?

  • 0 over 4 years ago in reply to Crispin_Ellisdon

    I did think that the F6 may be the accurate one and older watches may not be at first, but then compared the OWS pace in an enclosed bay with zero current or swell with that of an open water pool swim (50m) and the latter was at the expected pace 1:50-2:00 /100, which is what my race results are usually around (timed via race chip).

    The swim dead reckoning calculation sounds like it might be the issue rather than GPS. As it seems to be off by the same margin most swims.  

    I've attached a short swim comparison as an example

  • 0 over 4 years ago in reply to Dr Phil

    Yes you're right my bad, I meant Iron Man 70.3 distance rather than olympic!    I did think that it might be a strong current slowing me down but have compared it in an enclosed bay with no wind or swell with the same results.    No I don't stop during swim. I've attached a short swim comparison for reference.

  • 0 over 4 years ago in reply to Sydney Ryan

    The first 2 photos are on a fenix 5, showing my normal pace. The latter two show the fenix 6 on my other wrist showing the pace that is currently repeatedly between 20-30 seconds per 100m off

  • 0 over 4 years ago

    Just been for a swim with my F6 and the wife's. One recording OWS the other Swimrun. Apart from the difference in the tracks (hopefully Garmin working on that and I am talking with them) you can see the distance is close enough for a 2km measured swim course:

    Had swims like this all through the NZ summer with only a rare bad one.

  • +1 over 4 years ago

    I’m so glad to see someone else post about this. I’m not the greatest swimmer at the best of times, but have consistently been at 1:45 to 1:50 pace open water for about 6 years. My first swims after lockdown (first open water for this watch) and I’m 2:10 to 2:20 pace! Was shocked I’d lost so much just in just a couple of months. However, I’ve noticed people who swim slower than me normally posting times quicker than me but there maps are quite jagged (like mine used to be on previous watches) where as mine are nice and smooth. Having read DC rainmaker reviews it suggest the accuracy is very good. I’m therefore thinking that maybe mine is now showing the correct pace, and my previous and other people’s watches are showing a faster pace then they are actually going! 

    It’s kind of a relief that I’ve not got slower if that’s the case! 

  • 0 over 4 years ago in reply to Fidgetbum

    Yes! That’s the same as mine.... my map is accurate and smooth but times are much slower. My stroke rate is showing as the same as my old watch too which makes me doubt the  distance accuracy more so.

    worth comparing to your pool times before settling that 2:20 is your normal pace though. I don’t believe that I’m 30 seconds per 100 slower in calm open water (with a wet suit). 

  • 0 over 4 years ago in reply to Sydney Ryan

    Remembering this thread, at the weekend I did a quick test of my 6X Pro Solar on one wrist and 5+ on the other. You can clearly see the 6X records a much better track that means my average pace is much slower and I accrue less distance. The watch that is correct is the 6X, even if the stats are not flattering.

    Fenix 6X Pro Solar https://connect.garmin.com/modern/


    Fenix 5+ https://connect.garmin.com/modern/activity/4236536782