Samsung has begun issuing a new firmware update for the Galaxy Watch to US & South Korean users. The R810XXU1CSG4 update comes in at just over 15MB in size and is available for both the 42mm and 46mm non-LTE variants. The main feature is the improved swimming tracking - the watch should now be able to better measure burned calories during swim sessions.
The other big change is the ability to disable automated sync for alarms from paired smartphones. This means you can choose to have separate alarms on your smartphone and smartwatch if that's your thing.
Installing the new firmware involves going to the Wearable app on your phone and checking for new updates. As usual, the update is rolled in stages so it may take it a while to reach every region.