The goggles suggest some common pool sizes when you are starting your pool swim. You can also choose your own custom length. 

Please note that the minimum pool length is 15 meters or 16.5 yards and the maximum is 650 meters or 710 yards for Pool Swim mode. For Workouts, the maximum pool size is 70 meters or 70 yards. 

If your pool is below this requirement, you can still use the goggles by choosing the Swim Spa mode on the goggles. You would use the non-partner swim spa option to see the following metrics:

• Time
• Real time stroke rate
• Heart rate or heart rate zone (with compatible heart rate monitor)
• Calories