Time lost after swim

Just bought the new Venu 3 a week ago. I also use it during my (almost) daily swim in a lake nearby. 

This morning when I came out of the water I noticed that the clock time was not ok. In stead of showing the actual 10:02 as it should have,  it was four hours behind and showed 06:02. 

After a sync with my phone it was ok again, but I have never had this issue with my previous Vivoactive 4.
I assume that it has something to do with time synchronization with GPS when there is no phone nearby. And we all know that GPS and water are not the best of friends, but in my view this should never happen.

Anyone here who had the same issue?

Greetings,
Leo