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Open water swimming

Former Member
Former Member over 4 years ago

A new Garmin 935 has measured my 1st open water swim incorrectly. It has measured a distance that is probably 30% of the distance actually swum. Please can you let me know what can be done about this and how the error can rectified. Very frustrating for a top of the range triathlon watch !

  • 0 over 4 years ago
    1. So, unfortunately the 935 which I have used for about 200 open water swims is not accurate when worn on the wrist unless you do straight line put and back swims.  I did a 1125 m triangle swim with the 935 on the wrist and a Locosys bgt31 GPS unit in my swim buoy. I compared the  track and individual data points of the 2 units.  The major difference is the fact that in 22 minutes the 935 only recorded 34 points.  Whereas the bgt31 recorded over 1400 points. The 935 recorded about 25% shorter disctance and the track showed obvious inaccuracy. Iwill put both units in the buoy next swim and compare again. 
    2. Until Garmin improve their chips and software for Open water swimming I will not be recommending them to any serious Open water swimmers.  Its demoralising to see your pace read 2.20/100 when you swim at 1.40/100m! Also the watches ain't cheap!! It's a shame because for land training the watch is excellent. 
  • 0 over 4 years ago

    So I have this same problem with the 935 too. Wearing my watch in the cap is annoying, plus the time is wrong because you can’t stop the watch during the swim. And it rips swim caps. And I can’t do it in a race.

    So really inconvenient…

    i wrote to Garmin support and they refuse to engage. Sent me a form letter with “tips”. 

    What now? Is this a secret marketing campaign for the Fenix 6?

  • 0 over 4 years ago in reply to Zylonne

    How do you put the Garmin under cap? Aren't you afraid to lose it? and inside buoys, in a plastic bag? Just wondering... Garmin gave me that option but I do not see how it is going to work. Thanks!

  • 0 over 4 years ago in reply to Kabuxa

    Hi Kabuxa - I secure the watch strap around my goggles strap, and position the watch so the face is at the crown of my head and facing upward.  That way the watch does not come off unless your goggles come off, and they are bound together.  You can do this over a cap, or put another cap on top of both your watch and goggles.  In either case, you have to start your session before putting it up on your head, so your times will be a bit off.   However, your GPS track will be accurate (don't forget to *NOT* use "open water swim" mode, but rather "walk" or "run" mode.  Good luck!

  • 0 over 4 years ago in reply to Rick

    Thanks a lot! Makes sense... the solution doesn't but... I told them the watch is to wear on the wrist not on the head... but they claimed that once it works fine like that, it will be automatically fixed when we use it properly  ;o))) What do you think?

  • 0 over 4 years ago in reply to Kabuxa

    Well, after lots of tests in lots of open water conditions, I can't get my 935 to provide accurate GPS readings if it is on my wrist in any mode, or if it uses "open water swim" mode when mounted on my head or in a bag.  The only situation where it gets kinda close is when I swim a straight line course along buoys, but in that case you don't need GPS - you already know where you are, how long the course is, and the buoys keep you on a straight course over ground even in a current.  Maybe you will have more luck.

  • 0 over 4 years ago in reply to Kabuxa

    I stick up the back of the cap and keep a goggle strap below it. This way, you can feel the button to start it. 
    I bought a 920xt on eBay and have been using it for awhile, it is much more accurate, almost the same as the watch in the cap.

  • 0 over 3 years ago

    Dear All, I have problems with my 935. Altimeter in activity is allways too high. Distance in open water swimming allways too short (app. 700m recorded for 1000m really). Do you think it can come from the firmware ? I have 21. Do someone have infos about the release date of the new one ? Thanks

  • 0 over 2 years ago

    Both mine and my wife's 935's started under-reading on swimming about 12 months ago. We haven't been swimming open water much so just assumed it was a GPS glitch. This month I started racing again so did some proper testing and have confirmed both watches are under-reading whether on the wrist or on a bouy. It's a solid >20% under read. I contacted Garmin and the best they could offer was a 30% discount on a new watch. Real shame that a £450 watch is no longer fit for purpose after 3 years... surely there is a software fix they could look into for the likely thousands of people with this issue?!