Watch Ultra Open Water Swim GPS Accuracy Problem

Dear Apple community,

I have been using the Apple Watch Ultra for two months to track my daily open water swim sessions. I live by the Aegean Sea, the weather is almost always perfectly clear and without clouds. Ultra performed perfectly accurate swim distance measurement every day for the last two months. However, for the last 5 days, it's not performing and measuring at least 500 meters extra every swim session. I usually swim around 1,5-2 kilometers with a pace of 1:50/100m. Now the Ultra is recording extra distance that I didn't swim and thus also recording my pace as 1:10/100m which is impossible for me. This is such a let down and disappointment. I bought this device just for the purpose of tracking my Open Water Swim sessions accurately. It worked well for the last two months but now not anymore and I have no idea how to get this fixed. I suppose it's not hardware but a software problem? I suppose it might have happened after the latest Watch OS software update. I don't know.

Apple we need your support asap!

Anyone else having the same issue?

(I swim together with a friend who has Watch 6, and his device has been recording perfectly accurate...)