Waterspeed on Apple Watch can read the Heart Rate frequency and Calories consumed in real-time, shows on the screen, and save on the track data. It also saves the activity in Apple Health with data and the Route, to help you to close your rings.

Please note that you can manually Export to Apple Health (Fitness app or apple Activity) from the Share icon inside a single track page.

if something is not working, please refer to this article: Heart Rate or Calories are not working