Garmin Water Navigation

[Francoise Witsell]

Ithen 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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Seapilot is a fairly comprehensive navigation app (though some of the more advanced features, like routing and weather forecasting, require upgrading to the premium version), which introduces a different twist into the mix: Facebook integration. Connected friends are displayed like AIS targets on the app, so finding each other and linking up on the water is easier. Seapilot is also unusual in that it can offer polar diagrams (which show the theoretical attainable speed depending on wind direction and speed) for over 300 boats, to determine the ideal path to steer a sailboat taking wind and current forecasts into account.

GPS systems have dramatically changed the way we navigate our world. Car-based GPS systems have made it easier than ever to get where one needs to go, without the need for complicated maps that do not change with the changing conditions of traffic or construction. GPS units have become invaluable for people in cars, on foot and even in the water.

For the marine enthusiast, GPS units can be incredibly useful - whether taking a leisurely boat ride or doing a little fishing. There are many different types of marine-specific GPS units that provide increasing levels of information, detail and sophistication, depending on the need of the user. These units can be pretty basic for the novice water enthusiast, or incredibly complex for the expert user.

These units, while they won't necessarily break the bank, do cost money and many do not understand the differences between different types of GPS units. A common question amongst novice water enthusiasts is whether or not the GPS system they use in their car will work on a boat.

Will Work for Limited Uses

A GPS unit will work anywhere that it can receive satellite transmissions, but an automotive unit will not be programmed with aquatic maps. This means that they provide limited utility on the water as they are not loaded with detailed topography, depth or shoreline maps. An automotive unit may be useful in helping determine a general location, but it is not designed to provide step-by-step water navigation.

One of the biggest disadvantages to using a car-based GPS is that it is not designed to withstand such conditions. This type of GPS is not made to be waterproof, durable or resistant to the elements as this is not the intended use. They were designed to withstand the conditions inside a car, not on the lake.

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