Hi Griffiths415,
Thank you for participating in the Apple Support Communities. We understand your watch is recording your freestyle as breaststroke when swimming. We recommend making sure your watch is set to the correct wrist as this can affect how the watch records your workout. This article explains how to change the orientation if needed: Change language and orientation on Apple Watch - Apple Support.
"If you want to move your Apple Watch to your other wrist or prefer the Digital Crown on the other side, adjust your orientation settings so that raising your wrist wakes your Apple Watch, and turning the Digital Crown moves things in the direction you expect.
- Open the Settings app
on your Apple Watch. - Go to General > Orientation.
You can also open the Apple Watch app on your iPhone, tap My Watch, then go to General > Watch Orientation."
If that's not the issue, this article has some steps that can help with getting the most accurate measurements: Get the most accurate measurements using your Apple Watch - Apple Support.
We hope this helps.
Take care.