Garmin Open Water Swimming

[Analisa Wack]

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GPS accuracy when recording an open water swim can be difficult to achieve since the GPS signal cannot travel through water and the watch is repeatedly submerged while swimming. When recording an open water swimming activity, following these best practices will ensure that the watch will provide the most accurate GPS information possible:

Depending on form and breathing pattern, it may be best to place the watch on the opposite wrist. Avoid strokes like the breaststroke and swimming underwater. If you stop swimming, keep the watch above the surface of the water and stop the activity timer. Try not to hold the watch underwater for more than 3-5 seconds.

Enabling a secondary satellite constellation allows for your watch to more quickly acquire a satellite fix, and can help maintain satellite connection while swimming in open water. For specific instructions on how to Enable a Secondary Satellite Constellation on your watch, refer your owner's manual.

Just received my Vivoactive 4 and am trying figuring out the functions. As this version now has heartreate monitoring for swimming I was hoping if not expecting the profile for outdoor swimming to show up. The indoor and outdoor versions are there for the other sports, so i'm clueless why an outdoor swimming (open water swimming) profile is missing. Heartrate in water is now measured, SWOLF detection is already there, gps is already there. Garmin please add this profile.

I Set my vivoactive 4 on bicycle mode and gives very good speed map and distance.Please note that I fin swimm facing up 300 strokes add then 30 crawl strokes for 1 km .When swimming facing up every 300 strokes I lift the watch hand for a minute so it CAN get the GPS SIGNAL.

Chest straps do not work under water unless they can buffer up data and send when out of water again. Garmin has such chest straps, but they are not supported by our watches. But try SUP for open water swimming. Then you get heart rate and some GPS data.

I then set out for a swim. In the main bay I was testing, there were channel/boat buoys, that I used as reference points and simply connected the dots. These allowed me to have relatively consistent testing each day as I was swimming the same route.

Ultimately, the VERTIX 1 won this battle easily, due to the RIVAL getting tripped up on satellite re-acquisition and adding phantom distances. Had it not done that, both GPS tracks would have scored fairly well.

Overall, the COROS VERTIX 1 put itself into the top tier category with this swim. Note that placing itself in this category has nothing to do with how it ranked against the other watch on the other wrist, but how it compared to the reference track and where I actually swam.

Ultimately, there was no obvious meaningful difference between either track when it came to the GPS plot itself, with only the actual distance being different (but no clear-cut way to decide a true winner). But I think anyone would be pretty happy with either of those GPS tracks, thus both units get placed in the top tier.

At first glance above and below, you might assume these were similar, but in reality, the Instinct Solar had some bobbles here, but again, through the magic of different distances than tracks, seemed to figure things out. More on that in a second.

So, wrapping up this one, the Apple Watch Series 6 easily gets into the top-tier bucket. Whereas the Instinct Solar is sorta a perplexing one. Once it decided to play along with my swim game, you can see it was spot-on. And technically it had good distance too. But obviously, it started late and also skipped chunks of the track, thus, it gets relegated to the mid-tier.

Now somewhat interestingly, both the Suunto 9 Peak and Forerunner 945 reported substantially different distances to the reference track (which was my swim buoy, swimming 1 meter to her side). This was interesting, because my two watch numbers (listed as Round 5 above) matched the swim buoy, but not hers. Yet, her FR945 GPS track visually matched virtually perfectly with the reference track. I have no logical explanation as to why this is. Seriously, I have no idea. But, I do know that the Suunto 9 Peak still produced oddities (note: The swim buoy track switched colors here to purple):

While at first glance things look similar on the straight-aways, there are some differences here from the VERTIX 2, especially when I made turns, you can see how the Vertix 2 got a bit wobbly. Also, you can see on the lower right side how it actually had lost GPS entirely, and just connected two dots between two points I treaded water.

The challenge is a bit of the weight. I probably could stick a GPSMap 65 inside the buoy, but in general, short of the rare scenario where the watch gets face-down in the water, my reference tracks usually come out exceptionally well.

The Fenix 5 Plus series actually did get a lot of fixes backported to it, as it had the GPS-track-stop issue too. In the case of the Fenix 5X Plus, the major swim-related fixes came in firmware version 8.01: link to www8.garmin.com

I sold my Fenix 5s plus 2 months ago and bought the Fenix 6 pro and since then I see a clear improvement in the GPS tracks during open water swimming. The Fenix 5s plus created long lines in the canal where I normally swim, and it looks like I am drunk. The Fenix 6 pro has way more datapoints and creates a more fair straight line.

Do you know if those firmware updates will be available for 935? With 21.00 the open water accuracy is simply rubbish. It is quite annoying to see how something that worked perfectly is useless since 2 years ago.

I think most of 935 users feeling is like we have been abandoned just because the product has been discontinued.

Hi Ray, if i swim a loop around small islands and so I see that my garmin fenix 6 pro sapphire is spot on with the gps track but its about a couple of 100 meters short on a 3400m swim. Also in Xterra 1500 it says 1350 (which matches your findings) in an Ironman 3800m swim its always short. Is it possible that the gps track is great but the calculations to distance is not? Maybe garmin can fix that in a firmware update?

Could anyone recommend a watch for swimming in front of a current generator like an endless pool? My instinct solar uses gps, and I am not doing any flip turns. Just swimming in one spot for thirty minutes. Is there anything that could estimate my yardage and track my heart rate?

I think that you will have to determine water speed at the surface yourself with each speed setting of the endless pool (filming a floating duck toy or such?) And just multiply your swimming time with the water speed at that setting to get a distance. In the browser version of Garmin connect you can then create a new workout. No watch required :)

When swimming front crawl, the breathing side wrist typically spends more time above the water, which could affect your results. I see you marked the Suunto9Peak track with the wrist it was worn on but not the others. Can you please mark the tests with the wrist they were worn on (left/right) and also what your breathing pattern was?

Interesting view of all the watches, I have recently bought a Garmin Swim 2

Which I find excellent, previously had a Suunto Ambit 3 sport which was a

nightmare, had problem with no GPS sent off it took 7 weeks to return, never

again buy a Suunto.. Happy with Garmin Swim 2. Woohoo.

Hi Ray,

thanks for the nice article, as always. One question: I also like to do open water swimming from time to time, however I prefer breaststroke. I guess this will not work with a watch on my wrist as it would be constantly under water, right? Did you ever try? (owning a Garmin Vivoactive 4 right now, I cannot test it. However I do use a swim buoy (inspired by you), so it is really not a big issue).

Greetings, Patrick

HI DC Rainmaker, do any of the watches measure water temperature? I like cold water swimming and that measurement is just as important as the swimming accuracy, since I am probably swimming in circles hoping to stay warm!

Noting the increased distance over the reference track appears to happen consistently with all the watches that operated through the whole test. Is it possible that the extra distance came from the arm swings into the air above water, much like we account for accents and descents in cycling distances?

Is there some kind of GPS-puck that you can connect to your watch for open water swimming? That way you could get all the swim-statistics on/from your wrist, but use GPS-data from the external GPS that you have either in your swim buoy or under the swim-cap. Something that can store the GPS-data and then merge with your workout, the same that you sync HR-data from your chest strap via bluetooth after you get out of the water.

Triangular courses are actually the easiest for watches, because the change in compass heading is easy for most watches to pick-up (at least, most watches made in the last few years). The act of a turn, assuming no underwear sections (e.g. crowding at a buoy), is the easy trigger point for most watches.

Thanks for your reply. I disagree however. Based on hundreds of open water swims, the Garmin 935 and Swim 2 always truncate the apices of triangles. Much more accurate in straight lines. The 935 records about 10% of the data points compared to a BTG31 ( both in a swim hat for that test). I even sent the 935 back and received a replacement.

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