Series 7 watch creating issue while swimming

Hi im using apple watch for the past 3-4 years. And for the last 24 months i have been using it while swimming. Recently i got updated to 7 series but the same has been creating trouble while in the pool.For the first 20 minutes it keeps on pausing on its own again and again.there is no software iodate pending for the watch or phone still the issue being coming up everyday.

kindly suggest