'Data recording' option for open water swimming

I haven't dug through a raw OWS FIT file but am fairly sure it is not recording GPS every second in this mode.  At least looking at the GPS points that I see plotted, they are clearly very randomly spaced out and at an interval >> 1 second (even >> the "normal" smart recording interval).

You have probably seen a few other threads around talking about OWS issues, I personally still believe the GPS firmware < 2.50 (or so) worked far better for me than 2.50+ (I can't recall with certainty that was the revision, but it was roughly 1 yr ago...).

It's also unfortunate because the 945 and F6 (different chipset, different firmware) seems to work head and shoulders above what the latest firmware for 935 is doing... at least in my personal limited experiences.

I've played with GPS, Galileo, Glonass and haven't seen any obvious fix in my environment and stroke.  I generally sit for minutes with a lock before starting and try to wait a few seconds out of the water before stopping.  I always do freestyle with roughly consistent timing.

I'm now mostly following along on these threads in case someone finds a better fix - maybe trying to revert GPS firmware via an old beta would be an interesting test (if it's possible to achieve).

I put the whole triathlon club on it and several have excellent tracking in the same lake, so it is NOT local difficulties getting satellite line-of-sight. Fenix 6, 5, and 3 gave good results. Another guy with a FR935 has a terrible tracking at the same lake.

Still, I seem to have better results in the fjord (open landscape) than at the lake (narrower). Does it make sense that if the FR935 is a tiny bit less efficient at finding satellites, it would manage in open fjord, but just not have time (while my wrist is above water) at the narrower lake?

And if the Fenix(es) are quicker they would manage no matter the landscape around?

I just swam this morning with a friend and a new guy. He was struggling with distance measurements as we went (he checked during breaks and it didn't make sense). As I asked him which watch he was using, he answered unsurprisingly  Forerunner 935...
I had reverted to having my watch in my buoy, in run mode. It gives a much higher density of gps points and automatically removes breaks. But you lose swim dynamics, water temperature, and you can't check during the workout, only after. And  all in all, that's not what you buy a relatively high end watch for.

Same with the Fenix 5. Last year I got decent OWS tracks, but this year they are useless.

Open water swim GPS fails. I have experienced all of the symptoms reported on the Garmin site. Here is what worked for me. Switched to 1 sec data recording to increase the likelihood of capturing data when your wrist is out of the water. Sync with the Garmin Connect within 2 hours prior to the swim to update ephemeris data. After starting the open water ap wait for a few minutes after the GPS says it’s ready before starting the swim timer. 

1. Its so reassuring that I'm not the only one having this issue! My 935 underestimates my sea swims by 25%. I have tried all permutations of SMART VS 1 second, GPS, GLONASS, Galileo.  Using it in a buoy. Nothing works.  I notice that its not as bad for straight line out and back swims but it lacks accuracy for triangle courses.
2. I contacted Garmin and they replaced my 935 with a refurbished 935. It is no better...
3. I compared it yesterday with a Locosys BGT31 (www.locosystech.com/.../gps-handheld-data-logger-gt-31.html) which  I put in a swim buoy and compared the results. The BGT made over 2000 data points in my 35 minute swim. The 935.....less than 30 data points!!
4. I'm not sure what to do next but I would like Garmin to see whats going on. 

The labelled photo is the locosys track. The other is the 935

This sounds very familiar, guy_mx99. Very few data point that cannot capture the details of a non-straight swim. However, the whole idea of a putting the watch in a swimbuoy is that you acquire data in "run mode", meaning that you get many data points. You lose the swim dynamics, you cannot start and stop for breaks, but the distance is very reasonable.