Short Rest detection is a function in the goggles that allows the classification of brief rest moments between fast swimming intervals. This is likely necessary for competitive level swimmers but is not usually needed for the average swimmer.  

Example: Swimming 100m intervals, completing them in 1 minute and 24 seconds with the next take off time set for 1 minute and 30 secs. The goggles will be identifying those 6 seconds difference as rest before starting the next interval.

To toggle this setting on or off, tap on the cog from the Home tab or your profile page, then on Short Rest Detection. If the toggle switch is greyed out, Short Rest detection is currently turned off.