I've been using Fenix 5X Sapphire for over three years now. Since this summer many friends and I have suffered problems with too short distances recorded in Open Water Swimming.
Garmin's advice: syncing with connect, 1s recording, hand above water DON'T RESOLVE the issue.
Attached is a photo of exactly the same OWS from July 2nd. Downloaded from the watch both the watch and Garmin Connect show distance 1595 meters. After downloading the GPX file to my computer and uploading it back to Garmin Connect, the distance is 100 meters longer 1690 meters. How does Garmin explain this? I assume the time difference between the same two files is explained by the file type. GPX ignores breaks/stops. It only shows timestamps.
If someone would like to have a deeper look, I've also attached two activities from two years apart. Both .FIT and .GPX. Two years ago the distances were far closer to correct than they are today.
@garmin: how do explain this? It's causing frustration among users including Fenix 5, Fenix 6, FR9xx and FR7xx
The .FIT & .GPX files may be downloaded
OWS July 12, 2019 FIT https://drive.google.com/file/d/14aG6CwAPnx4Was0It0AXvppiLoWOmG3t/view?usp=sharing
OWS July 12, 2019 GPX https://drive.google.com/file/d/1KWcqCftNOp19k0toEy_VGa0vfdt3b-0E/view?usp=sharing
OWS July 5, 2021 FIT https://drive.google.com/file/d/1xkQ070zb7jCVfQN_dyBTc0Dz6ZbDOhzx/view?usp=sharing
OWS July 5, 2021 GPX https://drive.google.com/file/d/1kn4_9wmX4w2RVoqbQJ_7raXdJ1dVEYLx/view?usp=sharing
