Syncing takes place over Bluetooth and is somewhat automatic. I can get back to my car after a dive and before I have changed out of my gear, my dive has already been synced to the cloud and I get a nice little notification that it's ready to view.
The major drawback of this environment is that an internet connection is required to not only sync the data to Garmin Connect but to even view anything more than a high level summary. The Garmin Connect Mobile app stores only summary data and the real data is stored in the cloud. This means that if you are in a remote location with no internet access, it is not possible to sync with Garmin Connect or view any dive data.