Auto Rest and Manual Rest
The auto rest feature is available only for pool swimming. Your watch automatically detects when you are resting, and the rest screen appears. If you rest for more than 15 seconds, the watch automatically creates a rest interval. When you resume swimming, the watch automatically starts a new swim interval. You can turn on the auto rest feature in the activity options (Activities and App Settings).
During a pool or open water swim activity, you can manually mark a rest interval by pressing LAP.