Open Water Swim activity not recording correctly

Your track is good indeed. I have trouble remembering for certain, but feel like GPS 2.50 on the 935 (and before) worked slightly better for me in Minnesota, USA area.

Here is a swim comparison from this morning doing laps along a ~200 yd swim area with my wife.  We swam different paces.  Based on her swim fitness I wonder if her's filtered out some distance from the corners - she is usually a little faster than this.

She has a fenix 6s Pro and I a 935.  In my case the 935 was now on GPS + GLONASS and I think her's GPS only.  In the past I always used GPS only with similar results.

What is especially odd to me is that her pace graph looks so much nicer than mine, the track plotted... I'd guess better (we first started across, then decided to do the swim area border).  Our stroke rate close enough that I'd guess our arms are out of the water very roughly the same amount of time.

I may bring an old Vivoactive and strap it to my swim buoy next time just to see how crazy mine looks compared to a 1s recording watch floating behind me.  I will also probably experiment with GPS + Galileo for the fun of data collection.

Hi, same problem with my FR935 since last update. Very bad GPS accuracy during open water activities. Settings : GPS only, 1s recording. I wait 5 minutes after first GPS fix before starting my swim session. My swim technique is technique is the same, only the watch firmware could explain this ... NB : Other activities are doing well (very good precision on running or biking activities).

I see the accuracy with latest 19.10 update about the same than last summer (whatever the version was then). I have swam several sessions by now in this summer and I have noticed only one really curious thing. I added CRTDatafields https://apps.garmin.com/en-US/apps/ed502057-1f8e-4e29-96be-fcbb55b3b552 to Open Water Swimming as additional data field to get watch to log the temperature more accurate than 1 degC (which is the built in logging accuracy). That make the logged GPS track much worse, actually it's like that I have been drunk so zigzagging here and there around the true path taken. Still, the total distance seems to be OK giving me 1:50ish/100m and actually the zigzag motion is not that bad but centre properly around true path. But, It seems that Strava is recalculating distance based on logged GPS+Galileo track and so overreports distance to be at least 1.5 times too long 

Without that additional data field the accuracy of recorded track seems to be just about same than last summer compared to my reference device Polar V800 on other wrist. FR935 seems in generally report about same or somewhat (0..10 %) less total distance than Polar and Polar track is always more "smooth" (it's like FR935 route is logged as sparse GPS points connected by straight lines and Polar logs dense GPS route appearing as smooth curvature along the FR more angular path). I use GPS+Galileo it that matter, no obvious reason but my general impression has been that setting provide best and most consistent OWS tracking. I also always wait proper GPS fix (after FR935 reports a fix I still wait 10s or so before pressing start) and end the activity by waiting about 10..20s with hands above surface before stopping the recording.

Below are couple recent sessions with and without additional CRTDatafields data field compared to Polar V800 routes on lefthand side. The exact routes taken on sessions 1 and 2 are not same but the total distance are about the same:

• Session 1: V800: 1756m FR935: 1666m
• Session 2: V800: 1790m FR935: 1632m

Session 1 with CRTDataFileds

Session 2 without CRTDatafields

this makes sense to me! I get the same GPS trace (zigzag) using a data field from Garmin IQ on the Open Water Activity, next time I will try to remove it and try again, thanks for the idea! I attached my GPS that seems so close to yours.

This was from a swim along a 2km measured course this morning. I've seen much worse tracks but the distance has been about the same. While I like to see nice tracks I'm more interested in the distance. I am lucky that I have a 2km course marked with buoys each 250m for reference.

And it really is that cold! But the sun was shining and the water a balmy 14C

Hello to all.

Fully disappointed from my new 935.Tried several times to swim in open water (sea) and the result was bad.Too many zig-zags and only the 25% of the total distance was recorded.Firmware 19.10....

This is my first Garmin forerunner tracker.

Should I deactivate the move iq feature in order to fix this problem?Did anyone tried this?Thank you in advance!

As a runner, I've had nothing but good success with the FR 935. However, just started open water swimming. My first two swims in a lake both resulted in distances and tracking for about half of what I actually swam. Disappointing. Not sure if I lost satellite or if the watch just assumed I was finished. I turned off the automatic lap feature (not that it will make any difference) for my next swim and see what happens. Running firmware 19.10. 

The tracking of most of my swims this season (one month) has been really bad and much worse than last season. Do Garmin read the posts here or should I complain in some other way? I want to have a watch with all features working.

An example where I actually swam an 800 m triangle, back and forth over the lake and a smaller triangle. I also had some pauses on land. The distance "measured" where about 1000 m longer than the actual distance.             

For anyone seeing issues with GPS, one thing to consider trying (may not do anything...) is turning off BLE (phone connection) before swimming.

I happened to swim with my phone in my drybag buoy and noticed an awful track.  Others noted Connect IQ datafields may impact things strangely..

So I decided to turn off BLE completely and then swam and had probably the best track I have seen in a year.  Maybe it's a one off luck, I will continue to experiment.