Hi, I'm the developer of Open Water Swim, and I have had multiple reports and have also confirmed with my own testing that the WatchOS 10 update has seriously degraded GPS data during open water swimming, both with the native Workout app and with Open Water Swim. The data provided by CoreLocation is no longer accurate or trustworthy. I will post several pictures showing before and after update swims: Here's the raw data (mapped) of a swim done with watchOS 9 on the Ultra. Same swim today: From another pair of users: These two went TOGETHER, one with watchOS 9 and one with watchOS 10. You can probably guess which is which. Watch OS 9 swim: SAME SWIM WITH A PARTNER ON WATCHOS 10 (beta here) And another, again, two people swimming together, one watchOS 9 and one watchOS 10. watchOS 9 Same swim, same time, watchOS 10 I have filed two feedback assistant reports with APPLE. One when it was still a beta issue: FB12587468. This one has zero response from apple. And now a second one filed with watchOS 10 release: FB13192409 Apple devs, I know you're here and listening, so please let's get this fixed ASAP. Thanks

Related to this thread https://developer.apple.com/forums/thread/737819 I can confirm (again) that GPS performance on the watch Ultra (and likely all watches on watchOS 10) had been severely degraded. Here is a swim that I did with both an Apple Watch Series 4 on watchOS 9 (green track) and a watch Ultra on watch OS 10.1 (blue track). While the Series 4 provides relatively accurate data, the Watch Ultra provides very poor data with criss crossing paths and ridiculous data points. Apple did respond to my feedback with the usual request for sysdiagnose but this has not progressed. FB13192409