Good things come in 3. 

See how much you move, exercise, and stand daily, and track every way you work out. Listen to your favorite music. Text, call, and email. Pay for lunch, and get a tap when it’s time to turn while getting directions. Series 3 lets you do it all, right from your wrist.

Keep motivated by tracking your daily activity on Apple Watch and seeing trends on iPhone
Measure workouts like running, walking, cycling, yoga, swimming, and dance, plus new tai chi and pilates
High and low heart rate notifications and irregular heart rhythm notification1
Emergency SOS lets you call for help from your watch2
Take calls and reply to texts, right from your wrist
View notifications at a glance on the Retina display
Sync music, podcasts, and audiobooks to your watch and enjoy them on the go
Swimproof design3
watchOS 8 features new workout types and enhancements to Messages
Apple Watch Series 3 requires an iPhone 6s or later with iOS 15 or later.

1Irregular rhythm notification requires the latest versions of watchOS and iOS. It is not intended for use by people under 22 years old or those who have been previously diagnosed with atrial fibrillation (Afib).

2To use Emergency SOS, your iPhone needs to be nearby. If your iPhone isn’t nearby, your Apple Watch needs to be connected to a known Wi-Fi network and you must set up Wi-Fi Calling.

3ISO standard 22810:2010. Appropriate for shallow-water activities like swimming. Submersion below shallow depth and high-velocity water activities not recommended.

Apple Watch Series 3, Aluminum Case with Sport Band, 42mm:

GPS and a barometric altimeter track how far and high you go
Apple Watch 42mm has a dual-core processor for faster app performance
Ultimate sports watch and intelligent activity tracker
Apple Watch aluminum case is appropriate for shallow-water activities like swimming in the pool or ocean
Even more intuitive and intelligent
Apple Watch 42mm includes an aluminum case
Measures: 42 mm
Color of this Apple Watch aluminum case: black gray and silver/white