After you have finished surfing, make sure to “Stop” the surf session on your watch. Synchronization will then automatically take place when your Apple Watch is within reach of your iPhone. Your Sessions data will be immediately available, but the syncing process may take up to five minutes.
If it is still not syncing, make sure your Apple Watch and iPhone are connected. You can do this by swiping up from the bottom on the home screen of your watch. A GREEN iPhone icon indicates your watch is connected and a RED icon indicates it’s not connected or paired correctly. (insert screenshots)